promotoren: prof. dr. g.j. meijer & prof. dr. r. koole

Frits Perdijk

Promotoren: Prof. dr. G.J. Meijer & Prof. dr. R. Koole

Colofon© 2012 Frits BT Perdijk, Wageningen, the Netherlands

ISBN 978-90-393-5826-9Cover: Arthur Perdijk 2012Drawing page 64 and 126: Viktor Perdijk 1999Lay-out and printed by: Print Service Ede

The role of distraction osteogenesisin the treatment of theatrophic mandible

De rol van distractie osteogenese bij de behandeling van desterk geslonken onderkaak(met een samenvatting in het Nederlands)

Proefschrift

ter verkrijging van de graad van doctoraan de Universiteit Utrechtop gezag van de rector magnificus, prof. dr. G.J. van der Zwaan, ingevolge het besluit van het college voor promoties in het openbaar te verdedigen op vrijdag 19 oktober 2012des middags te 12.45 uur.

door

Frederik Bastiaan Teunis Perdijk

geboren op 18 augustus 1949te Rotterdam

Promotoren:Prof. dr. R. KooleProf. dr. G.J. Meijer

Het drukken van dit proefschrift werd mede gefinancierd door:

Prof. dr. P. Egyedi Stichting ter bevordering van de Mondziekten, Kaak- & Aangezichtschirurgie, Utrecht.

J. Laverman Tandtechnisch Laboratorium, Ewijk

Goedegebuure Tandtechniek, Ede

Implantologie groep Neder-Veluwe

Seres Accountants en Belastingadviseurs, Bennekom

Van Straten Medical Nederland, Nieuwegein

Paranimfen:Drs. J. Th. van VlietDr. W. van Vree

Manuscriptcommissie:Prof. dr. J.A. Dhert (voorzitter)Prof. dr. R.M. CasteleinProf. dr. C. de PutterProf. dr. G.M. RaghoebarProf. dr. P.J.W. Stoelinga

Contents

Introduction .................................................................................................................................................... 9

Chapter 1 Distraction osteogenesis and aim of the study. ..................................... 23

Chapter 2 Implants in the severely resorbed mandibles: ........................................ 31 whether or not to augment? What is the clinician’s preference?

Chapter 3 The use of intra-osseous versus extra-osseous ...................................... 49 distraction devices in atrophic mandibles.

Chapter 4 Complications in Alveolar Distraction .......................................................... 63 Osteogenesis of the Atrophic Mandible.

Chapter 5 Effect of extra-osseous devices designed for .......................................... 79 vertical distraction of extreme resorbed mandibles on backward rotation of upper bone segments.

Chapter 6 The lower border augmentation technique to allow ......................... 91 implant placement after a bilateral mandibular fracture as a complication following vertical distraction osteogenesis; a case report.

Chapter 7 Summary, conclusions and future perspectives. .................................. 99

Chapter 8 Samenvatting, conclusies en toekomstperspectief. ........................... 109

List of publications .................................................................................................................................................... 119

Dankwoord .................................................................................................................................................... 125

Curriculum Vitae .................................................................................................................................................... 131

Introduction

11

Introduction

1. Introduction

1-1. Aetiology of bone resorptionBone is a complex, living tissue, constantly being renewed. The architecture and composition of cancellous and cortical bone allow the skeleton to perform its essential mechanical functions. The stiffer cortical bone responds more slowly to changes in load, while cancellous bone has a much larger surface area per unit volume and a greater rate of metabolic activity. The periosteum covers the external surface of bone and consists of two layers: an outer fibrous layer and an inner more cellular and vascular layer. 1 The inner osteogenic layer or cambium layer can form new bone, while the outer layer forms part of the insertions of tendons, ligaments and muscles.

The bone matrix has an organic component: primarily type I collagen, which gives it tensile strength and an inorganic component: primarily hy-droxyapatite, which provides stiffness to compression. Specialized populations of bone cells form, maintain and remodel this matrix. Four types of bone cells are recognized, based on their locations, morphology and functions: osteopro-genitor cells, osteoblasts, osteocytes and osteoclasts. Osteoprogenitor cells develop from undifferentiated cells and subsequently develop into osteoblasts, while osteocytes are formed from osteoblasts. Osteoclasts have a separate stem cell line: blood-borne monocytes. Bone matrix apparently attracts these monocytes and stimulates their differentiation into osteoclasts.

The process of bone modelling and remodelling requires osteoclastic resorption of bone matrix and deposition of a new matrix by osteoblasts. Mod-elling shapes and reshapes bones during growth and stops at skeletal maturity. Physiological remodelling does not change bone shape and consists of bone resorption, followed by bone deposition in approximately the same location. Since it continues throughout life, it appears to be important for maintenance of the skeleton. 2 Adaptive remodelling is the response of the bone to altered loads and may alter the strength, density and shape of bone. 3 Mechanical loading is a particularly potent stimulus for bone cells, which improves bone strength and inhibits bone loss with age. Bone accumulates damage from loading but is capable of self-repair. The molecular mechanisms by which bone adapts to loading and repairs have implications for bone health, disease and the feasibility of living in weightless environments (e.g. spaceflights inducing bone loss). 4 A number of stimuli affect bone turnover including hormones, cytokines and mechanical stimuli.

On a cellular level the osteocytes are considered to be bone mechano sensory cells, that translate mechanical signals into biochemical bone metabo-lism, regulating stimuli necessary for adaptive remodelling. Loading of bone induces deformation of the hard bone matrix. Consequently, the changed flow of interstitial fluid through the lacuna-canalicular porosity seems to activate the osteocytes by enhanced release of prostaglandin E2 and nitric oxide and reduced release of transforming growth factor-β. It also

12

leads to osteocytic cell death and less osteoblastic activity. This concept explains local bone gain and loss. 6 7 In particular osteoporotic (female) patients with an imbalance between bone resorption and bone formation, caused by changes in calcium-regulating hormones and reduced osteocyte numbers, might have imperfect bone remodelling resulting in a lack of bone mass and strength.

1-2. Post-extraction remodelling and classification of edentulous jawsFollowing tooth loss, the mandible may undergo substantial remodelling. There is great individual variety in the rate of resorption, with some people losing little bone, while others undergo fast resorption. In addition, women show more resorption than men. It is, therefore, understandable that several studies have been published on this topic. Cortical thickness and density (mass per unit volume) have been measured in various studies. Kingsmill and Boyde (1998) concluded there was a significant increase in bone density of edentulous individuals as well as an increase with age. 8 Schartz-Dabney and Dechow (2002) found, by comparing the structural base of bone of edentulous and dentate patients, differences in cortical thickness, elastic and shear noduli, anisotropy and orientation of the axis of maximum stiffness. This suggests changes in the cortical microstructure following loss of teeth. 9

It was John Hunter’s observation of the “waste of the sockets of the teeth” in the 1750s, that prompted him to consider bone as a material capable of remodelling rather than the immutable and permanent structure it had previ-ously been thought to be. 10

In 1892 the German surgeon Julius Wolff proposed: “mechanical stress is responsible for determining the architecture of bone”. Remodelling of bone occurs in response to physical stress or to the lack of stress. This means, that bone is maintained in sites subjected to stress and is resorbed in sites, where there is little stress.

Tallgren (1972) reported, that 3 to 5 mm of loss of height occurred of the alveolar ridge within the first 3 months following tooth extraction. The process then continues at a slower rate. She also noted, that the amount of bone loss in the mandible is usually four times greater than in the maxilla. 11

During the initial healing phase after the teeth are lost, the sockets are filled with a blood clot. Osteoprogenitor cells from the ruptured periodontal ligament differentiate into osteoblasts, invade the coagulum and form woven bone, 12 which is later replaced by cancellous bone. The crest of the residual ridge narrows and the sharp edges of the alveolar processes are reduced. 13 As the bone is reduced in height by periosteal osteoclastic resorption, there is an accompanying endosteal apposition, but at no time is new bone formation seen on the periosteal surface of the residual ridge, which remains porous, never developing a complete cortical layer. 14 15 Further internal remodelling results in a loss of organization and

13

Introduction

a thinning of the trabeculae as well as disruption of the arrangement of the lamellar and Haversian systems. 5

Several attempts to classify the resorption pattern of the residual alveolar ridge of the mandible have been made. The most commonly used were developed by Atwood, 16 describing different types of alveolar atrophy and the Cawood & Howell classification, which is based on accurate measurements. 17

They analysed patterns of alveolar resorption from a sample of 300 dry skulls. It was noted that, whilst the shape of the basal part of the mandible and maxilla remains relatively stable, changes in the shape of the alveolar process were highly significant in both the vertical and horizontal direction. Based on this study, a classification was put forward, which identifies six stages of resorption. Class I and II describe the pre- and post-extraction situation respectively. Class III represents a rounded ridge with an adequate height and ridge sufficient for placement of a dental prosthesis. Class IV represents a knife-edge ridge with adequate height but inadequate width. Class V represents a flat ridge with both an inadequate height and width and Class VI a depressed ridge. This classification was subsequently extended by Stoelinga et al., who added two more stages: Class VII and VIII (Fig. 1). 18 The Cawood & Howell classification shows different resorption patterns in the incisor, pre-molar and molar regions. In the pre-molar and molar regions the inferior alveolar nerve may even become exposed on top

Figure 1: Classification of the edentulous jaw according to Cawood, extended by Stoelinga.

14

of the residual ridge. This is the reason that patients wearing dentures on these severely resorbed mandibles are sometimes complaining of pain.

1-3. Facial appearance of edentulous patientsResorption of the alveolar ridges leads to changes in the relationship of the jaws, oral mucosa, muscles and alterations in facial morphology. 19 In the horizontal plane the majority of the bone loss occurs from the buccal aspect in the maxilla, resulting in a reduction in palatal width and length as well as height. 20 In the mandible most of the bone loss takes place from the labial aspect anteriorly and from the lingual aspect posteriorly. The maxillary arch becomes increasingly narrower and the mandibular arch becomes broader. The arch width of the edentulous mandible is on average 7 mm greater than the edentulous maxilla , measured immediately anterior to the retromolar pads and tuberosities respectively. Through both the resorption of the maxillary and the mandibular ridge the interarch distance increases. Consequently, by autorotation of the mandible, the lower facial height , the distance measured between point Nasion and Gonion, shortens. As a result the chin rotates foreword (“witch chin”) especially in Cawood & Howell class V and VI patients.

The muscles of facial expression are responsible for man’s facial ap-pearance. Most of these muscles are located in the midface and around the mouth. These muscles are inserted into the skin and underlying bone of the facial skeleton as well as the maxilla and mandible. Resorption of the jaws leads to a reduction in and distortion of the muscle fibres. As a result, the or-bicularis oris and depressor and levator muscles collapse inwardly, resulting in a diminished commissure width and thin lips. 21

Inside the mouth, the attachments of the circumoral and floor of the mouth muscles become increasingly superficial, as bone loss progresses. The vestibular fold flattens and the floor of the mouth tends to bulge. The attached, keratinised mucosa shrinks with progressive bone loss as well. Ill-fitting dentures may sometimes cause hyperplasia of the mucosa because of constant pressure of the denture flanges, resulting in an epulis fissuratum. 22

Figure 2: Changing facial appearance due to loss of teeth.

15

Introduction

1-4. Functional and psychological consequences of edentulism Loss of natural teeth leads to impaired chewing ability. The wearing of full dentures is associated with a significant deterioration of most, if not all, oral functions, even if the dentures are technically perfect. Patients may complain about their inability to eat and about pain, due to the pressure on the soft tis-sues. Their sense of taste may also be affected. Most of these complains are the result of instability and reduced retention of the lower denture. However, 85% - 90% of patients receiving new and technically well-made dentures and 65% - 75% of patients with older dentures, are generally satisfied with the treatment result. It is likely to be more of a tribute to human adaptation to the changed situation than to prosthodontic skills. 23

Psychological factors seem to be extremely important in the acceptance of and adaptation to removable dentures. Loss of teeth, and, therefore, loss of body image can result in anxiety, depression or both and can affect a patient’s adaptive capacity to accept edentulism and complete dentures. Three types of maladaptive responses are considered as probable consequences of fear, anxiety and depression associated with tooth loss and complete dentures. In maladaptive class 1, the patient adapts physically, but is maladaptive psychologically, thus, suffering some impairment of quality of life. In class 2, the so-called “difficult patient” is maladaptive physically and psychologically and keeps the dentist involved technically and emotionally for a protracted period of time. The class 3 patient is devastated by the loss of teeth. Physical and emotional maladaptibility are accompanied by much suffering and social withdrawal. 24 In a study of dissatisfied denture patients, it was shown that these patients feel more inhibited in their social contacts and are more often of the opinion, that wearing dentures is unacceptable. These patients are also highly neurotic, less socially adequate, more rigid, have less self-esteem and are more internally oriented. 25 26 Satisfaction with dentures for most patients is individually determined and is often unpredictable for the dentist and patient. 27

The above considerations, both from a functional and psychological point of view, are probably the reason why patients and referring dentists try to improve denture stability, retention and aesthetics. This has led to the devel-opment of preprosthetic and later preimplant surgery.

2. Conventional preprosthetic surgery

Several techniques have been developed over the years to enlarge the denture bearing area so as to improve denture stability and retention. Depending on the state of resorption, these techniques may be classified as relative or absolute augmentations. The relative augmentations include vestibuloplasties and lowering of the floor of the mouth, using split skin or mucosal grafts. Absolute augmentation implies true heightening of the ridge, using bone grafts or even alloplastic material, notably hydroxylapatite.

16

2-1. Relative augmentation Szabo (1916) described first a vestibuloplasty using a horizontal incision in the mucosa on the top of the residual ridge of the symphyseal area of the mandible. The mucosa was dissected supra periosteal and downwards and sutured to the periosteum at a lower level. The exposed periosteum, between the top of the ridge and the sutures were left uncovered or covered by a pre-operatively made base plate or modified prosthesis, that was fixed by perimandibular wires. The exposed periosteum was eventually covered by secondary epithelisation. Relapse of the deepening of the vestibulum often occurred due to contraction and reattachment of the dissected muscles. This was the reason why surgeons soon began to use split skin grafts to cover the exposed periosteum, which resulted in more stable results. 29 Others followed, using mucosal grafts, either taken from the palate or cheek. 30 31

Several modifications of the vestibuloplasty, using pedicled flaps, which were thinned and reattached to the periosteum, have also been described by Kazanjian in 1924, 32 Pichler and Trauner in 1930 33 and Edlan and Mejchar in 1963. 34

Deepening of the lingual fold was achieved by dissecting the mylohyoid and the upper parts of the genioglossal muscles. The lingual mucosa, including the muscles attached to it, were fixed at a lower level, using matrass sutures that were brought around the mandible towards the buccal vestibule, where they were tightened. This could be combined with a vestibuloplasty. In all cases the exposed periosteum both on the lingual and the vestibular side were covered by split skin graft. (Obwegeser 1963). 35 The introduction of mucosal grafts by Propper (1964), Steinhauser (1969) and Tideman (1972) avoided the need for taking skin grafts with consequent scar formation and donor site morbidity 36 37 38

Obwegeser (1953) reported on a sub-mucosal vestibuloplasty in the maxilla. Through a vertical midline incision in the anterior vestibulum, the underlying, redundant sub-mucosal tissue was removed, thus, deepening the buccal fold. The gained vestibular depth was maintained , using a base plate or adapted denture. 39

2-2. Absolute augmentation When the residual bone height was less than 15 mm, augmentation of the man-dible was often carried out. Various methods have been used, including onlay and interposed bone grafts.

2-2-1. Onlay graftsSplit-thickness rib grafts 40 or autogenous bone from the iliac crest has been used as an onlay grafts on the residual ridge of the atrophied mandible. 41 42 Fixation of the grafts to the mandible was done by circumferential steel wires or lag screws. 43 Onlay bone grafting has proved to be unsatisfactory because of almost complete resorption of the graft, when a conventional denture

17

Introduction

was worn. 49 Due to donor-site morbidity, other materials for grafting have been tried. Bone substitutes, such as blocks of hydroxylapatite 44 or allogeneic bone have been used. Particulate material has also been used in sub-periosteal tunnels or injected in resorbable Vicryl® tubes on top of the edentulous ridge. The graft material, however, tends to migrate to the lingual and vestibular areas, or may cause pain due to pressure on the mental or even inferior alveolar nerve. Mucositis, hyperaemia and swelling of the overlying mucosa are often associated with soreness. Dehiscences or perforation of the mucosa may also occur, resulting in infection.

2-2-2. Visor osteotomy Because of the poor results achieved with onlay augmentations, other methods have been developed. The visor osteotomy, as proposed by Härle (1975), 45 made use of the width of the resorbed mandible by splitting it in two halves. The lingual part was put on top of the buccal part, thus, increasing the vertical dimension of the mandible. 46 This, however, resulted in a knife-edge ridge. Damage to the alveolar inferior nerve resulting in paraesthesia or even anaes-thesia in the chin area, often occurred.

2-2-3. Sandwich osteotomySchettler (1976) introduced the sandwich osteotomy , which was limited to the symphyseal area. 47 Through horizontal splitting of the mandibular bone between the mental foramina and interposing a bone graft, a substantial augmentation could be achieved. Various modifications of this technique have been described during subsequent years, including mixing the particular bone grafts with bone substitutes. Considerably less bone resorption has been reported, using this method, as compared to the onlay graft techniques 49 50 51

In general , augmentation of the atrophied mandible was followed by a second procedure, including vestibuloplasty and/or lowering of the floor of the mouth.

3. Preimplant surgeryWith the introduction of endosseous implants, a revolution in the art of pros-thetic dentistry has occurred. Implants provide excellent stability and retention for prosthetic devices, provided they are placed in strategic positions. For this reason preimplant surgery is often necessary, particularly for the class IV- VI mandibles. 52 This type of surgery has evolved from conventional preprosthetic surgery, but is largely focussed on creating enough bone volume to place im-plants in optimal positions.

Techniques such as onlay and interposed bone grafts may still be used to create sufficient bone volume for implant placement. It is particularly the onlay graft that has become popular. Its reliability has

18

been greatly enhanced by the introduction of rigid fixation. 53 Initial healing of the grafts is secured by this type of fixation, while maintenance of the augmented bone is secured by the forces exerted by the loaded implants.

The original onlay and sandwich techniques have been slightly modified so as to adapt to the needs of the partial or complete edentulous patients. A typical example is the lower border bone graft, which was sometimes used in the conventional preprosthetic surgery era. 44 45

All techniques, involving harvesting bone grafts, have a serious disadvantage in that donor side morbidity will always be present. Research has been focussed on replacing autogenous grafts by bone substitutes. Progress has been made in this area and applications in selected cases have shown good results. This is particularly the case when these materials are used for limited defects and are combined with membranes that allow for undisturbed bone ingrowth.56

An alternative way to circumvent donor site morbidity includes the use of distraction osteogenesis. Some studies on the feasibility of this technique in the context of preimplant surgery are included in this thesis.

19

Introduction

Reference

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8 Kingsmill VJ, Boyde A. Variation in the apparent density of human mandibular bone with age and dental status. J Anat. 1998 Feb;192 ( Pt 2):233-44.

9 Schwartz-Dabney CL, Dechow PC. Edentulation alters material properties of cortical bone in the human mandible. J Dent Res. 2002 Sep;81(9):613-7.

10 Cohen B. John Hunter, pathologist. J R Soc Med. 1993 86:587-592.11 Tallgren A. The continuing reduction of the residual alveolar ridges in complete

denture wearers: a mixed-longitudinal study covering 25 years. J Prosthet Dent. 1972 Feb;27(2):120-32.

12 Roberts WE, Chase DC (1981). Kinetics of cell proliferation and migration asssociated with orthodontically induced osteogenesis. I Dent Res 60:174-181.

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14 Pudwill ML, Wentz FM (1975). Microscopic anatomy of edentulous residual alveolar ridges. J Prosthet Dent 34:448-455.

15 Neufeld 10 (1958). Changes in the trabecular pattern of the mandible following the loss of teeth. J Prosthet Dent 8:685-697.

16 Atwood DA, Coy WA. Clinical, cephalometric, and densitometric study of reduction of residual ridges. J Prosthet Dent. 1971 Sep;26(3):280-95.

17 Cawood JI, Howell RA. A classification of the edentulous jaws. Int J Oral Maxillofac Surg. 1988 Aug;17(4):232-6.

18 Stoelinga PJW, Blijdorp PA, De Koomen HA; Augmentation of the atrophic mandible with interposed bone grafts and particulate hydroxylapatite. J Oral Maxillofac Surg 44:353,1986.

19 Cawood JI, Howell RA. Reconstructive preprosthetic surgery. I. Anatomical considerations. Int J Oral Maxillofac Surg. 1991 Apr;20(2):75-82.

20 Likeman PR, Watt DM (1974). Morphological changes in the maxillary denture bearing area. A follow-up 14-17 years after tooth extraction. Br Dent 1 136:500-503.

21 Watt DM, MacGregor AR (1986). Designing complete dentures. 2nd ed. Bristol: Wright.

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22 Bhaskar SN. Synopsis of Oral Pathology. 425-426. 4th edition. Mosby 1973. Saint Louis.

23 Berg E. Acceptance of full dentures. Int Dent J. 1993 Jun;43(3 Suppl 1):299-306. 24 Friedman N, Landesman HM, Wexler M. The influences of fear, anxiety, and depression on the patient’s adaptive responses to complete dentures. Part I. J Prosthet Dent. 1987 Dec;58(6):687-9.

25 Moltzer G, Van der Meulen MJ, Verheij H. Psychological characteristics of dissatisfied denture patients. Community Dent Oral Epidemiol. 1996 Feb;24(1):52-5.

26 al Quran F, Clifford T, Cooper C, Lamey PJ. Influence of psychological factors on the ac-ceptance of complete dentures. Gerodontology. 2001 Jul;18(1):35-40.

27 van Waas MA. Determinants of dissatisfaction with dentures: a multiple regression analysis. J Prosthet Dent. 1990 Nov;64(5):569-72.

28 Szabo J. Methode zur Verhinderung des Verwachsens der durchtrennten Mundschleimhaut. Öst.-ung.Vierteljahresschr. Zahnheilk 1916;32:244.

29 Schuchardt K. Die Epidermistransplatation bei Mundvorhofplastik. Dtsch Zahnärtzl Z1952;7:364-369.

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31 Tideman H. Vestibulum plastiek met het vrije mucosa transplantaat. Acad Thesis. University of Amsterdam 1973.

32 Kazanjian VH. Surgical operations as related to satisfactory dentueres. Dental Cosmos 1924;66: 387-395.

33 Pichler H, Trauner R. Die Alveolarkammplastik. Z Stomatol 1930;38:675-697.34 Edlan A, Mejchar B. Plastic surgery of the vestibulum in periodontal surgery for

better den-ture service. Int Dent J 1963;13:593-96.35 Obwegeser HL. Die totaleMundbodenplastik. Schweiz Monatschr Zahnheilk

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cheek. Int J Oral Surg 1972;1:76-80.39 Obwegeser H. Alveolarkammplastik im Unterkiefer. Zahnärtzl Praxis 1953;4.40 Steinhäuser E, Obwegeser HL. Rebuilding the alveolar ridge with bone and

cartilage auto-grafts. Transactions of the 2nd Int Conference of Oral Surgery. Munksgaard, Copenhagen, 1967; 203-208.

41 Thoma KH, Holland DJ. Atrophy of the mandible. Oral Surg Oral Med Oral Pathol 1951;4:1477-1495.

42 Wang JH, Waite DE, Steinhäuser E. Ridge augmentation: an evaluation and follow up re-port. J Oral Surg 1976;34:600-602.

43 Beckers HL, Freitag V. Fixation of onlay bone grafts with lag screws. J Maxillofac Surg. 1980 Nov;8(4):316-23.

44 Kent NJ, Quinn JH, Zide MF, Finger IM, Jarcho M, Rothstein SS. Correction of alveolar ridge deficiencies with non-resorbable hydroxylapatite. J Am Dent Assoc 1982; 105: 993-1001.

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45 Härle F. Visor osteotomy to increase the absolute height of the atrophied mandible. J Maxil-lofac Surg 1975;3:257-260.

46 Mercier P, Cholewa J, Djokovic S, Masella R, Vinet A. Mandibular ridge augmentation and resorption with various visor procedures. J Oral Maxillofac Surg. 1982 Nov;40(11):709-13.

47 Schettler D. Sandwich technique with cartilage transplant for raising the alveolar process in the lower jaw. Fortschr Mund Kiefer Gesichtschirurgie 1976; 20:61-63

48 Stoelinga PJ, Blijdorp PA, Ross RR, De Koomen HA, Huybers TJ. Augmentation of the atrophic mandible with interposed bone grafts and particulate hydroxylapatite. J Oral Maxillo-fac Surg. 1986 May;44(5):353-60.

49 Fazili M, Overvest-Eerdmans GR, Vernooy AM, Visser WJ, von Waas MA. Follow-up investigation of reconstruction of the alveolar process in the atrophic mandible. Int J Oral Surg. 1978 Aug;7(4):400-4.

50 Lekkas K. Absolute augmentation of the mandible. Int J Oral Surg. 1977 Jun;6(3):147-52.

51 Satow S, Slagter AP, Stoelinga PJ, Habets LL. Interposed bone grafts to accommodate en-dosteal implants for retaining mandibular overdentures. A 1-7 year follow-up study. Int J Oral Maxillofac Surg. 1997 Oct;26(5):358-64.

52 Cawood JI, Stoelinga PJ, Blackburn TK. The evolution of preimplant surgery from prepros-thetic surgery. Int J Oral Maxillofac Surg. 2007 May;36(5):377-85. Epub 2007 Mar 30. Re-view.

53 Stoelinga PJW, Cawood JI. Fundamentals of bone grafting in implantology. In: Ferri J, Hun-ziker EB. Ed: Preprosthetic and maxillofacial surgery. Biomaterials, bone grafting and tissue engineering. Cambridge : Woodhead Publishing Limited, 2011:25-35.

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Distraction osteogenesis and aim of the study.1

25

Distraction osteogenesis and aim

of the study.Chapter 1

1-1. Distraction osteogenesisDistraction osteogenesis is a biological process of new bone formation between the surfaces of bone segments, that are gradually separated by incremental traction. 1

The principles of mechanical manipulation of bone segments have been practised in orthopaedics since ancient times, when Hippocrates described the placement of traction forces on broken bones. He used an external apparatus consisting of two leather rings around a broken lower limb, which could be manipulated by applying tension and fixated afterwards. 2

In the 14th century, Chauliac described a technique of continuous traction for long bone fractures, using a pulley system, that consisted of a weight attached to the leg by a cord. 3

In 1905, Alessandro Codivilla introduced surgical practices for lengthening of the lower limbs. He used external skeletal traction after an oblique osteotomy of the femur.

Figure 1: External fixator according to Hippocrates.

Figure 2: Limb lengthening according to Codivilla.

26

Professor Gavriil Abramovich Ilizarov developed distraction osteogenesis in the 1950s. He treated patients with fractures and non-unions following World War II in the Kurgan region of Siberia, and later in the Soviet Union. Without the benefit of antibiotics, Ilizarov was able to cure cases of chronic osteomyelitis using only this method.

Ilizarov discovered two biological principles of distraction osteogenesis known as “Ilizarov principles”.

• The first Ilizarov principle postulates, that gradual traction creates stress, that can stimulate and maintain regeneration and growth of living tissues.

• The second Ilizarov principle theorizes, that the shape and mass of the bones and joints are dependent on an interaction between mechanical loading and blood supply.

The Ilizarov procedure comprises four phases: (1) corticotomy and placement of an external fixation system (2) latency period (3) distraction and (4) consolidation. 4 5 6

Ilizarovs work was introduced to Italy in the 1980s and later to the USA, as a result of the former Soviet Union’s policy of “glasnost” (openness). In 1992, the application of craniofacial distraction osteogenesis was introduced by McCarthy et al. 7 They treated children with congenital craniofacial anomalies with extraoral distraction devices. Around the same time, Guerrero reported on mid-symphyseal widening of the mandible with a tooth-borne hyrax-type device. 8 Miniaturization of the distraction devices and the introduction of intra-oral devices improved the possibilities of distraction osteogenesis in the craniofacial area. In 1996, Chin and Toth reported the first clinical application of vertical mandibular alveolar distraction osteogenesis. 9

Figure 3: Gavriil Abramovich Ilizarov. Academician of the Russian Academy of Medical Sciences. 1921–1992.

27



1-2. Distraction osteogenesis in atrophic mandiblesAll augmentation procedures with autogenous bone grafts require a donor site. Rib grafts, calvarian bone grafts, tibial grafts and iliac crest grafts are commonly used. These donor sites may have complicated healing. Harvested free bone blocks will remodel, due to the activity of the osteoclast and osteoblast cells and ingrowth of blood vessels. Osteodistraction deals with the formation of vital bone, it is likely to be an attractive method for reconstructing the alveolar ridge height. The technique of osteodistraction of the atrophied mandible consists of a segmental osteotomy between both mental foramina. Surgery is carried out under general anaesthesia. A horizontal incision is made on the vestibular surface of the lower lip, and the alveolar process is exposed according to a modified Edlan method. The mucoperiosteum is only displaced on the vestibular side. Lingually, the mucosa remains attached to the bone, so that the part of bone to be distracted obtains its blood supply via the lingual side. The mental nerves are identified on both sides. Eventually, using a reciprocal saw, the horizontal and vertical osteotomies are carried out. After separating the bone segments, the distractor device can be placed and tested to ensure that the transport segment can be raised properly. The surgery is completed by reattachment of the mucoperiosteal flap, leaving the adjustment nut of the distractor device visible intra-orally. After a latency period of 6 days, distraction is initiated, depending on the device which is used, at a rate of mainly 0.5 mm a day. On completion of distraction, confirmed radiographically, a consolidation period starts of about 12 weeks. Hereafter dental implants can be installed and the distractor device removed. The advanced miniaturized distraction devices used nowadays for distraction of the mandible can be divided into two categories: extra-osseous and intra-osseous distractor devices.

1-2-1. Extra-osseous distraction devices

Figure 4: Extra-osseous distraction device (Mondeal®).

28

Extra-osseous distraction devices (Fig. 4) are placed sub-periosteally on the lateral aspect of the alveolar bone. These devices can be used for transportation of alveolar segments with teeth as well as edentulous segments. They usually consist of a frame with spindle and additional mini-plates for fixation on the basal and the transport segment. 10 11

1-2-2. Intra-osseous distraction devicesThe intra-osseous distraction devices (Fig. 5) are inserted in the alveolar bone and are therefore mostly only suitable in the edentulous bone ridge. 12 13 From the concept of an intra-osseous device, a few systems have been developed to combine the distraction procedure with a dental implant in the same device. 14 In these cases, the top of the distraction device can be used to attach a suprastructure for dental reconstruction or attachment of a bar with overdenture.

1-3. Aim of the studyThe aim is to examine if vertical distraction osteogenesis (VDO) is a valuable treatment in cases of extreme mandibular atrophy.

The following objectives are therefore investigated in the treatment of patients suffering from extremely resorbed mandibles:

• Which therapy is the clinician’s first choice when restoring the edentulous mandible? (chapter 2)

• Does the intra-osseous device (IOD) show better results compared with the extra-osseous device (EOD) as an augmentation method? (chapter 3)

• What complications are associated with VDO conducted with an EOD? (chapter 4)

• What is the vector of distraction using the EOD? (chapter 5)

Figure 5: Intra-osseous distraction device according to Krenkel®

29



Reference

1 Samchukov ML, Cherkasin AM, Cope JB: Distraction osteogenesis: history and biological basis of new bone formation. In Lynch SE, Genco RJ, Marx RE, editors: Tissue engineering: applications in maxillofacial surgery and periodontics, Carol Stream, III, 1998, Quintessence.

2 Peltier LF. External skeletal fixation for the treatment of fractures. In:Fractures: a history and iconography of their treatment, San Francisco, 1990, Norman Publishing.

3 Peltier LF. A brief history of traction, J Bone Joint Surg 50A: 1603, 1968.4 Ilizarov GA. The principles of the Ilizarov method: Bull Hosp Joint Dis. 1988;48:1-115 Ilizarov GA. The tension–stress effect on the genesis and growth of tissue: Part

1.The influence of stability of fixation and soft tissue preservation. Clin Orthop Rel Res. 1989;283:249-281.

6 Ilizarov GA. The tension–stress effect on the genesis and growth of tissue: Part 2. The influence of the rate and frequency of distraction. Clin Orthop Rel Res. 1989; 239: 263-285.

7 McCarthy JG, Schreiber J, Karp N, Thorne CH, Grayson BH. Lengthening the human mandible by gradual distraction. Plast Reconstr Surg 89: 1-10, 1992.

8 Guerrero CA: Expansian rapida mandibular. Rev Venez Ortod 1-2:48, 1990.9 Chin M, Toth BA. Distraction osteogenesis in maxillofacial surgery using internal

devices: Review of five cases. J Oral Maxillofac Surg 1996;54:45-5310 Hidding J, Lazar F, Zöller JE. Knockenregenration des Unterkieferalveolarfortsatzes

mit Hilfe der Vertikalen Kallusdistraction. Dtsch Zahnärztl Z 54:51, 1999.11 Perdijk FBT, van Strijen PJ. Augmentation of Severe Mandibular Atrophy by

Vertical Distraction Osteogenesis. In Samchukov M, Cope J, Cheraskin A (eds): Mandibular Distraction Osteogenesis. St Louis, MO Mosby 2001; 433-437

12 Raghoebar GM, Liem RS, Vissink A. Vertical distraction of the severely resorbed edentulous mandible: a clinical, histological and electron microscopic study of 10 treated cases. Clin Oral Implants Res. 2002 Oct;13(5):558-65.

13 Krenkel C, Grunert I. The Endo-Distractor for preimplant mandibular regeneration. Rev Stomatol Chir Maxillofac. 2009 Feb;110(1):17-26.

14 Gaggl A. Distraction implants. In Jensen OT. Ed : Alveolar Distraction Osteogenesis, Chicago, Quintessence Publishing Co, Inc, 2002; 119-132.

This chapter is an edited version of an article;Implants in the severely resorbed mandibles:whether or not to augment? What is the clinician’s preference?

Oral Maxillofac Surg (2011) 15:225–231

Frits B. T. Perdijk Gert J. Meijer Ewald M. BronkhorstRon Koole

Implants in the severely resorbed mandibles:whether or not to augment? What is the clinician’s preference?2

33

Implants in the severely resorbed m

andibles. What is the clinician’s preference?

Chapter 2

2-1 IntroductionAs the dimension of the alveolar ridge is dictated by the presence of teeth, their absence induces alveolar bone resorption. In the case of complete edentulism, replacement of the natural teeth by a denture does not stop the process of continuous bone resorption. In the contrary, as a result of the unfavourable forces introduced by the denture itself, resorption of the alveolar ridge is accelerated. 1 Lack of retention of the denture, pain, eat and speech difficulties, reduced facial height, relative prognathism, collapse of lower facial soft tissue with consequential altered appearance are the common problems, that patients have to deal with.

Endosseous implants increase the stability of the denture, thereby solving a part of above mentioned problems. However, installing implants is only feasible, if adequate alveolar bone volume is present. In case of extreme resorption of the mandible, the choice of treatment how to restore a deficit in bone volume, is still subject of discussion. Many strategies with their own specific advantages and disadvantages have been published . 2 3

As such, for example, sulcoplasties have been proposed; by lowering of the muscular attachments of the lip, eventually in combination with releasing the mylohyoid muscle, the denture bearing area of the mandible can be enlarged. 4 5 6

To increase the mandibular bone volume, various augmentation procedures such as onlay 7 8, sandwich 9, visor 10 or submental 11 approaches have been suggested, using an autologous bone graft or bone substitute as augmentation material. An alternative approach is the technique of alveolar distraction osteogenesis, creating an increase in bone volume without the use of bone substitutes or bone grafts. 12 13 14 15 16 17 An interesting topic is, at what point the bone volume is still thought to be sufficient to allow implant placement and at what point it isn’t. Nowadays, there is a tendency to use shorter implants, thereby, reducing the indication for augmentation procedures. 18 19

Aim of this study was to survey which procedure, related to the extremely resorbed mandible, is preferred at the present time. The extremely resorbed mandible was defined as a mandibular height in the symphyseal area of 12 mm or less, as measured on a standardized lateral cephalogram (Fig.1). At what mandibular height, the clinician decides not only to install implants, but also to perform an augmentation procedure. Does age of the surgeon, location of former training and present professional setting influence the choice of treatment? Is there a tendency to add more implants, when the residual ridge decreases in height?

To survey, which therapy clinicians prefer in case of an extreme resorbed mandible, a questionnaire was sent to all Dutch Oral- and Maxillofacial surgeons. Besides questions about education and experience, all surgeons were asked to treat five virtual edentulous patients, presenting various mandibular heights.

34

2-2 Material and methodsQuestionnaires were sent to all 198 OMF-surgeons, working on 58 hospitals housing departments of OMF Surgery in the Netherlands. Of these 129 surgeons (65%) responded.

The questionnaire comprised two parts; the first dealt about ‘age’, ‘location of former training’ and ‘present professional setting’, such as university, general hospital or private practice. Questions were asked about the surgeons preference for a certain surgical strategy in case of a resorbed edentulous mandible (see questionnaire part I).

To further inventory the surgeons preference, in the second part of the questionnaire, five imaginary complete edentulous patients were presented; the only parameter that varied was the mandibular height. Patient 1 represents a residual bone height in the symphyseal area of 15 mm, patient 2 of 12mm, patient 3 of 10mm, patient 4 of 8mm, and patient 5 of 6mm. All virtual patients were in good general health, edentulous, showing a small zone of attached gingiva in combination with a shallow vestibular sulcus. Of course, all patients suffered from retention problems of their dentures. Schematic cross-sections were depicted to represent the atrophic mandibles, as is shown by the Lateral Cephalometric Radiography: bone height varied from 15-6 millimetre (Fig.1). The OMF-surgeon was challenged to make an adequate treatment plan for these virtual patients.

Figure 1: Edentulous patient: RH = residual height in symphyseal area. In this study varying between 15 and 6 mm.

35



Chapter 2

The surgeon was faced up to choose or solely for inserting implants or to execute an augmentation procedure in advance (see questionnaire II). In addition, the preferred number of implants was asked for as also the method of augmentation. In the latter case, it was inventoried if autologous bone was liked superior than bone substitutes.

2-3 StatisticsFor data analysis the statistical analysis software package SPSS 16.0.01 was used. An independent sample-t-test was applied to analyse the relation between differences in treatment plans and ‘age of the surgeon’. All other background properties of the OMF-surgeons were coded as nominal variables and, therefore, the relation between these and differences in treatment plans were analysed using the Chi-square test, supplemented with the Fisher’s exact test.

2-4 ResultsRegarding the first part of the questionnaire, the mean age of the respondents was 46.5 years, ranging from 29 to 62 years. Most (78.6%) were working in partnership in a general hospital. Respondents were allowed to choose more treatment possibilities for the same patient. Therefore, percentages may exceed 100% (Fig. 2-5).

Bone augmentation methods

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Fig.2: Different bone augmentation methods used by Dutch OMF-Surgeons in cases of insufficient mandibular bone height.

Figure 2: Different bone augmentation methods used by Dutch OMF-Surgeons in cases of insufficient mandibular bone height.

36

Number of implants in cases of sufficient bone height

2 0

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Fig. 4: Number of implants placed in the edentulous mandible.Figure 4: Number of implants placed in the edentulous mandible.

Autogenous bone from

80

81 3 1 3

0102030405060708090

cris

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iaca

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Fig.3: The choice of Dutch OMF-Surgeons to harvest autologous bone grafts.Figure 3: The choice of Dutch OMF-Surgeons to harvest autologous bone grafts.

37



Chapter 2

The sulcoplasty, as a single surgical method to improve patient’s satisfaction, is hardly used anymore. However, in combination with or as a secondary procedure after implant placement, the sulcoplasty has still an important role (52% of the respondents uses this method incidental, 18% regularly). To improve the available bone volume, 57 % of the respondents are in favour of the onlay method (Fig.2). As second best, the sandwich method is regularly used (10%). Only few colleagues are in favour of the submental method (5%) or the visor osteotomy (4 %).

To harvest an autologous bone graft, 80% of the respondents are in favour of the (anterior) iliac crest as donor site. Only sparsely the tibia (1%) or cranium bone (1%) is chosen (Fig.3).

As a bone substitute Bio-Oss® is used regularly (39%), Cerasorb® sometimes (12%) and other bone substitutes hardly ever.

As an augmentation technique, only few colleagues use vertical distraction regularly (12%) or incidentally (23%). Intra osseous distraction devices are more popular (19%) than extra osseous ones (3%).

For the edentulous mandible with sufficient bone height, placing two permucosal dental implants at the position of the former canines is preferred by most of the respondents (96%). However, also the option of three, four and six interforaminal placed implants was selected (Fig.4).

A bar suprastructure with overdenture is the first choice (78%), followed by ball attachments (63%). Fixed bridgework is not often indicated in the Netherlands (8%) (Fig.5).

With respect to the second part of the questionnaire, all five virtual patients, as presented, suffered from an atrophic mandible, a small zone of attached gingiva, a small vestibular sulcus and an insufficient retention of

Suprastructure

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Fig.5: Suprastructure on implants in the edentulous mandible.Figure 5: Suprastructure on implants in the edentulous mandible.

38

their lower dentures. The following results were found (fig.6):

Patient 1. Complete edentulism, bone height symphysis area 15 mm.Most surgeons inserted two implants (85%). Others preferred three (6%), four implants (7%) or six implants (1%) (Fig.6). Sulcoplasty, as single therapy, was only chosen by one surgeon.

Patient 2. Complete edentulism, bone height symphysis area 12 mm.Again most surgeons inserted two implants (65%), as others inserted three implants (10%), four implants (14%) or 6 implants (1%). In this case 10 % of the surgeons preferred to augment the mandible in advance of implant placement using autologous bone as an onlay graft (Fig.6).

Patient 3. Complete edentulism, bone height symphysis area 10 mm.Also in case of a mandibular height of 10 mm, placing solely implants, is the first choice for 60% of the surgeons; most inserted two implants (28%), others three implants (11%), four implants (19%) or even six implants (1%) (Fig.5). Already 40% of the surgeons were in favour of an augmentation procedure in advance of implant placement; 28% for the onlay procedure, 6% for the sandwich method, 2% for the submental augmentation and 4% for the distraction procedure.

Patient 4. Complete edentulism, bone height symphysis area 8 mm.The majority of the respondents (71%) were in favour of first augmenting the mandible; 52% preferred the onlay procedure, 10%, the sandwich method, 4% the submental augmentation and 5% the distraction procedure. Just installing two implants without pre-implant surgery was suggested by 11% of the surgeons, three implants by 4% and four implants by 13% of the colleagues (Fig.6).

Patient 5. Complete edentulism, bone height symphysis area 6 mm.Only 9% of the respondents choose for implant placement without augmentation procedures; 2% preferred the option of two or three implants, 5% choose for four implants. The majority (91%) liked to improve the vertical height in advance of implant placement (Fig. 5); with an onlay graft (64.1%), sandwich method (8%), submental augmentation (8%) or vertical distraction (2%).

Statistical testingNeither ‘age of surgeon’ nor the variables ‘location of former training’ and ‘present professional setting’ showed a statistical significant relation with the choices made in the five patients, with one exception: in patients with a mandibular height of 10 mm OMF-surgeons, educated in Amsterdam and Groningen, preferred to insert implants, whereas the OMF surgeons trained at other locations favoured to augment the mandible first (p=0.029).

39



Chapter 2

Fig. 6: The choice of Dutch OMF-Surgeons to place 2, 3, 4 or 6 implants or to first restore the available bone volume in relation to the vertical residual bone height

Figure 6: The choice of Dutch OMF-Surgeons to place 2, 3, 4 or 6 implants or to first restore the available bone volume in relation to the vertical residual bone height

2-5 DiscussionIn the Netherlands, for implant surgery patients are referred to the OMF-surgeon. After implant placement, the prosthetic rehabilitation is executed by the referring dentist; therefore also the choice of suprastructure is in his hands. The first treatment of choice is installing just two implants, as is shown in the present study. This approach is less time consuming, easy to perform with relatively low costs. In the Netherlands each person is obliged to be insured for medical costs. In addition, the option of placing two interforaminal implants, the suprastructure and denture inclusive, is covered by the health insurance. Based on surveys of current literature, a consensus statement corroborates that there is now overwhelming evidence, that a two-implant overdenture should be the first choice of treatment for the edentulous mandible. 20 Surprisingly, in other countries for example Sweden, mainly implant-borne fixed restorations are placed in the edentulous mandible. This phenomenon is mainly explained by the generous Swedish dental insurance system, making fixed restorations available to most patients. The higher rate of edentulism and a more established tradition of removable dentures in the Netherlands comparing to Sweden, may further explain the differences in treatment between the two countries. 21 To date, the Dutch insurance companies reimburse most costs of implant overdentures in edentulous people, whereas there is no reimbursement for fixed restorations. This may explain the preference in choice for treatment; for a relative simple overdenture in the Netherlands versus complete pre-implant rehabilitation using augmentation procedures in combination with fixed and sometimes immediate loaded appliances in other countries .22 23

The outcome of the questionnaires shows, that the sulcoplasty, as single surgical method, is hardly used anymore. Nowadays, the most favourable approach, to restore retention of a denture, is to insert two implants. From review of the literature, it seems evident that many treatment concepts, involving mandibular overdentures supported by endosseous

40

implants, are based on empirical experiences or are merely based on opinions of members of individual centres. 22 If the patient desires increased stability of the mandibular denture and improved chewing ability, two implants, connected by a bar in the interforaminal region and supporting an overdenture, are sufficient as a general rule. However, when using only two implants a rotational movement of the denture is still feasible, because the denture is supported by both the mucosa and the implants. To increase the stability of the denture, more implants can be placed, thereby making the denture completely implant-borne. 24

This article inventories, at what mandibular height, clinicians choose for first executing an augmentation procedure before installing implants (Fig 6). In case of a mandibular height of 12 and 15 millimetre, both in the questionnaire as in the treatment of the virtual patients, the majority of the respondents prefer the option of inserting solely two implants. In case of a vertical bone height of 10 mm the choice for first performing an augmentation procedure became real. Already 40% of the respondents choose for augmenting the mandible previous to implant placement. The other 60% were in favour of just installing implants. About the topic at what mandibular height an augmentation procedure is required, literature is not conclusive. Although numerous studies have described the outcome results of dental implants in the edentulous mandible, few prospective studies have been designed as randomized clinical trials, that compare different treatment modalities, to restore the severely resorbed mandible. As such, in a prospective study Stellingsma et al (2004) compared three treatment methods in patients with an average mandibular bone height of 9,7+/-1,4 millimetre. 24 In one group they installed four short implants; in another group first an onlay procedure was performed, after which four regular sized implants were placed in a secondary procedure. In the latter group 10% of the implants have been lost, compared to 0 % in the group of installing just four short implants. Also retrospective studies 25 26 showed acceptable survival rates of between 92-94% after ten years of loading, using at least four short implants to support a fixed implant-supported prosthesis or overdentures. In the study of Deporter et al, (2002) overdentures were supported by three short implants showing a survival rate of 93% after 10 years. 27 The question pops up if these successes also will be achieved, if installing just two implants.

For the virtual patient, having a low mandibular height (6 or 8 mm), a minority of the respondents (29% and 9% respectively) choose for solely implant placement. Besides the risk of implant loss, the mandible may also fracture. However, this risk is relatively low. Recently an inventory by Soehardi et. al. of the number of fractures, that occurred in conjunction with implants, placed in edentulous patients in the Dutch population during the period 1980-2007 elucidated an incidence of only 0.033% . 28 Nevertheless, it was stressed that, if a fracture does occur, this complication is difficult to treat. 16 28

41



Chapter 2

To improve the available bone volume, most of the respondents are in favour of the onlay method, using iliac crest bone. The disadvantage of harvesting a bone graft is obvious; it demands an extra operation, resulting in a prolonged operation time, extra costs and more morbidity. Therefore, a shift to using short implants is a logical next step.

An interesting point is the age of the surgeon: it did not influence the choice whether “to augment or not”. This means that older surgeons evaluated their therapies to the present state of art in pre-implant surgery and also that younger surgeons have probably less acquaintance to “older” techniques like sulcoplasties, visor or sandwich augmentations. Surprisingly, the “location of training” was of significant influence. Surgeons trained in education clinics, who advocate the placement of short implants, followed the same strategy in the treatment of the virtual patient with a mandibular height of 10 millimetres.

Although numerous studies have described the outcome results of dental implants in the edentulous mandible, few prospective studies have been designed as randomized clinical trials, that compare different treatment modalities. There is a tendency to insert short implants in case the mandibular height in full edentulous patients is even lower than 10 millimetres. In a recently published case report even four implants with a length of only 5.5 mm length were placed in an extreme resorbed mandible (Lopez et al, 2009) . 29

To bypass the co-morbidity, that is linked to augmentation procedures using autologous bone, future prospective studies should concentrate on the issue, if placement of only two implants is a reliable option for the extreme resorbed edentulous mandible, having a residual height of less than 10 millimetres.

In conclusion, 12 mm residual bone height in the symphyseal area is the turning point for most of the colleagues, whether to perform augmentation procedures or solely place implants. On-going research in favour of placing short implants will decrease this turning point, maybe even to a level of 8 mm residual bone height or less, thereby reducing costs and patient morbidity.

42

Reference

1 Tallgren A (1972) The continuing reduction of the residual alveolar ridge in complete denture wearers; a mixed longitudinal study covering 25 years. J Prosthet Dent 27:120-132.

2 Jennings DE (1989) Treatment of the mandibular compromised ridge : A literature revieuw. J Prosthet Dent 61:575-579.

3 McCord JF, Grant AA, Quayle AA(1992) Treatment options for the edentulous mandible. Eur J Prosthodont Resto Dent 1:19-23.

4 Szabo J (19160 Methode zur Verhinderung des Verursachens der durchtrennten Mundschleimhaut. Öst.-ung.Vjschr. Zahnheilk 32:244.

5 Tideman H (1973) Vestibulum plastiek met het vrije mucosa transplantaat. Dissertation. University of Amsterdam

6 Hall HD (1971) Vestibuloplasty,mucosal grafts (palatal and buccal). J Oral Surg 29:786-791.

7 Neukam FW, Scheller H, Günway H (1989) Experimentelle und klinische Untersuchungen zur Auflagerungsostoeplastiek in Kombination mit enossalen Implantaten. Z Zahnärtzl Implantol 5:235-241.

8 Verhoeven JW. Cune MS. Terlou M. Zoon MA. De Putter C (1997) The combined use of endosteal implants and iliac crest onlay grafts in the severely atrophic mandible: a longitudinal study. Int J Oral Maxillofac Surg 26: 351-357.

9 Stoelinga PJW,Tideman H, Berger JS, Koomen HA de (1978) Interpositional bone graft augmentation of the atrofic mandible: A preliminary report. J Oral Surg 36:30.

10 Härle F (1975) Visor osteotomy to increase the absolute height of the atrophied mandible. A preliminary report. J Maxillofac Surg. 3(4):257-60.

11 Gutta R, Waite PD (2007) Cranial bone grafting and simultaneous implants: A submental technique to reconstruct the atrophic mandible. Br J Oral Maxillofac Surg 29

12 Ilizarov, G. A (1989)”The tension-stress effect on the genesis and growth of tissues. Part I. The influence of stability of fixation and soft tissue preservation. Clin.Orthop. 238: 249-81.

13 Chin M, Toth BA (1996) Distraction osteogenesis in maxillofacial surgery using internal devices:revieuw of five cases. J Oral Maxillofac Surg.54: 45-53.

14 Perdijk FBT,van Strijen PJ (2001) Augmentation of Severe Mandibular Atrophy by Vertical Distraction Osteogenesis. In Samchukov M, Cope J, Cheraskin A (eds): Mandibular Distraction Osteogenesis. St Louis, MO Mosby pp 433-437

15 Hidding J, Lazar F, Zöller JE (1999) Initial outcome of vertical distraction osteogenesis of the atrophic alveolar ridgeMund Kiefer Gesichtschir. 3 Suppl 1:S79-83

16 Raghoebar GM, Heydenrijk K, Vissink A (2000) Vertical distraction of the severely resorbed mandible. The Groningen distraction device. Int J Oral Maxillofac Surg. 29(6):416-20.

17 Krenkel C, Grunert I (2009) The Endo-Distractor for preimplant mandibular regeneration. Rev Stomatol Chir Maxillofac. 110(1):17-26.

18 Stellingsma K, Raghoebar GM, Meijer HJ, Stegenga B (2004)The extremely resorbed mandible: a comparative prospective study of 2-year results with 3 treatment strategies. Int J Oral Maxillofac Implants. 19(4):563-77.

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Chapter 2

19 Adell R, Lekholm U, Rockler B, Brånemark PI (1981) A 15-year study of osseointegrated implants in the treatment of the edentulous jaw. Int J Oral Surg. 10(6):387-416.

20 Feine JS, Carlsson GE, Awad MA, Chehade A, Duncan WJ, Gizani S, Head T, Lund JP, MacEntee M, Mericske-Stern R, Mojon P, Morais J, Naert I, Payne AG, Penrod J, Stoker GT, Tawse-Smith A, Taylor TD, Thomason JM, Thomson WM, Wismeijer D (2002) The McGill consensus statement on overdentures. Mandibular two-implant overdentures as first choice standard of care for edentulous patients. Montreal, Quebec, May 24-25, 2002. Int J Oral Maxillofac Implants 17(4):601-2.

21 Carlsson GE, Kronström M, de Baat C, Cune M, Davis D, Garefis P, Heo SJ, Jokstad A, Matsuura M, Närhi T, Ow R, Pissiotis A, Sato H, Zarb GA (2004) A survey of the use of mandibular implant overdentures in 10 countries. Int J Prosthodont 17(2):211-7.

22 Batenburg RH, Meijer HJ, Raghoebar GM, Vissink A (1998) Treatment concept for mandibular overdentures supported by endosseous implants: a literature review. Int J Oral Maxillofac Implants. 13(4):539-45

23 Stellingsma C, Vissink A, Meijer HJ, Kuiper C, Raghoebar GM (2004) Implantology and the severely resorbed edentulous mandible. Crit Rev Oral Biol Med 15:240-248.

24 Stellingsma C, Meijer HJ, Raghoebar GM (2000) Use of short endosseous implants and an overdenture in the extremely resorbed mandible: a five-year retrospective study. J Oral Maxillofac Surg 58:382-387.

25 Friberg B, Gröndahl K, Lekholm U, Brånemark PI. Long-term follow-up of severely atrophic edentulous mandibles reconstructed with short Brånemark implants. Clin Implant Dent Relat Res. 2000;2(4):184-9.

26 Triplett RG, Mason ME, Alfonso WF, McAnear JT. Endosseous cylinder implants in severely atrophic mandibles. Int J Oral Maxillofac Implants. 1991 Fall;6(3):264-9.

27 Deporter D, Watson P, Pharoah M, Todescan R, Tomlinson G. Ten-year results of a prospective study using porous-surfaced dental implants and a mandibular overdenture. Clin Implant Dent Relat Res. 2002;4(4):183-9.

28 Soehardi A, Meijer GJ, Manders R, Stoelinga PJW. An inventory of mandibular fractures associated with implants in atrophic edentulous mandibles; a survey among Dutch OMF-surgeons. Int J Oral Maxillofac Implants (accepted).

29 Lopes N, Oliveira DM, Vajgel A, Pita I, Bezerra T, Vasconcellos RJ.A new approach for reconstruction of a severely atrophic mandible. J Oral Maxillofac Surg. 2009;67:2455-9.

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Questionnaire I.

Name ..................................................................................................................................................

Age ...................................... (Please. mention age in complete years)Trained as an Oral and Maxillo Facial Surgeon in:................................................................Operative: Private practice Hospital University Other:

My treatment of the atrophic edentulous mandible is:(As commentary you can write for example: too difficult, no experience, old fashioned, many complications etc.)

Regularly Sometimes Never % of the casescommentary

Sulcoplasty ........................................................................

Augmentation techniqueOnlay method ........................................................................

Sandwich method ........................................................................

Visor method. ........................................................................

Via submental ........................................................................

........................................................................

........................................................................

45



Chapter 2

I use autogenous bone harvested from: #Crista iliaca ........................................................................

Anterior or posterior ridge ........................................................................

Visor method. ........................................................................

#Tibia ........................................................................

#Cranium ........................................................................

#other: ........................................................................

I use bone substitutes, such as: Bio-Oss ........................................................................

CerasorbOssaturaOther: ........................................................................

Vertical distraction:# Intra osseous device ........................................................................

# Extra osseous device ........................................................................

Name of the distraction device youuse: ...............................................................

46

My choice in a case of edentulous mandible with sufficient bone height is:

Regularly Sometimes Never % of the casesPermucosal dental implants

1 ........................................................................

2 ........................................................................

3 ........................................................................

4 ........................................................................

5 ........................................................................

6 ........................................................................

Suprastructure

# Steg/bar ........................................................................

# Ball attachments ........................................................................

# Fixed crown and bridges ........................................................................

47



Chapter 2

Questionnaire II.

Below, the cross-sections in the canine region of five edentulous mandibles are depicted. Give your choice of treatment.All patients are in good general health, without any contra indication to any treatment. Intra orally a small zone of attached gingival combined with a small vestibular sulcus can be observed. All patients complain about loss of retention of their dentures

Questionnaire II. Below the cross-sections in the canine region of five edentulous mandibles are depicted. Give your choice of treatment. All patients are in good general health, without any contra indication to any treatment. Intra orally a small zone of attached gingival combined with a small vestibular sulcus can be observed. All patients complain about loss of retention of their dentures

Patient 1 Patient 2 Patient 3 Patient 4

Height 6mm Patient5 Note for each patient your preferred method of treatment Treatment: □ Sulcoplasty

□ Augmentation with autogenous bone, followed by dental implant placement

□ Onlay method □ Sandwich method □ sub-mental method

□ Augmentation with bone substitute, followed by dental implant placement

□ Onlay method

Height

15 mm

Height

12 mm

Height

10 mm

Height

8 mm Heig

6 mm

Note for each patient your preferred method of treatmentTreatment: Sulcoplasty

Augmentation with autogenous bone, followed by dental implant placement Onlay method Sandwich method Sub-mental method

Augmentation with bone substitute, followed by dental implant placement Onlay method Sandwich method Sub-mental method

Vertical distraction, followed by dental implant placement.

48

ONLY dental implant placement 1 implant 2 implants 3 implants 4 implants 5 implants 6 implants

Other/ comments: ..........................................................................................................................................................................................................................................................................................................................................................................................

...................................................................................................................................................................................................................

This chapter is an edited version of an article;The use of intra-osseous versusextra-osseous distraction devices in atrophic mandibles.

Int. J. Oral Maxillofac. Surg.2012; 41:521-526

F. B. T. PerdijkG. J. Meijer Ch. KrenkelR. Koole

The use of intra-osseous versusextra-osseous distractiondevices in atrophic mandibles3

51

The use of intra-osseous versus extra-osseous distraction devices.Chapter 3

3-1 IntroductionTo make implant placement possible in the extreme resorbed mandible, vertical distraction osteogenesis (VDO) has been introduced as a technique for bone generation. By first making a horizontal osteotomy in the interforaminal area, the upper segment is moved slowly upwards, allowing formation of bone tissue (callus) within the gap region. By using VDO, harvesting bone transplants can be avoided.

After 10 years of widespread application of VDO in the alveolar ridge, there is still significant disagreement about various treatment parameters, such as surgical technique, type of distraction device and minimal bone height necessary to perform the distraction.15 With respect to the type of device, two main philosophies have been introduced: the extra-osseous distractor (EOD) and the intra-osseous distractor (IOD). 18 There are only a few articles comparing EODs and IODs with each other.18 6 19 In these studies, however, miscellaneous patient groups were included, with atrophied alveolar ridges in the maxilla or mandible, in fully as well as partially edentulous situations.

An EOD mainly consist of a frame with a spindle, which is fixed with plates and screws on the buccal aspect of the bone. EODs are capable of transporting the osteotomized bone segment, irrespective of whether teeth are present or not. 7 10 An IOD, generally, has a pin-like configuration, that perforates the osteotomized segment, that is to be distracted. 12 8 This limits its use to only the fully or partially edentulous alveolar process. Modifications have been introduced, in which the IOD itself could be used secondarily as a dental implant. 3

3-2 Materials and MethodsAll fully edentulous patients, who were treated at two clinics with a VDO device, to enlarge the available bone volume to allow for implant placement, were included in this study. At the Paracelsus Medical School, Salzburg, Austria, patients underwent osteodistraction with an IOD (Endo-Distraction Krenkel®, Mondeal®, Tuttlingen, Germany: Fig. 1) and at the Gelderse Vallei Hospital, Ede, the Netherlands, patients underwent osteodistraction with an EOD (Mondeal Vertical Distraction® device Mondeal®, Tuttlingen, Germany; Fig. 2). Both groups were retrospectively surveyed. Data were collected on sex, age at operation, preoperative and postoperative bone height, gained bone height, tilting of the distraction device and complications like fractures, anchorage loss and sensory disturbances.

52

3-3 Surgical technique

For both distractor types, installation was performed under general anaesthesia. First, a horizontal incision was made on the vestibular surface of the lower lip, to expose the alveolar process according to a modified Edlan method. A mucoperiostal flap was reflected only on the vestibular side, leaving the periosteum in place on the alveolar crest. The lingual mucosa remained attached to the bone, thereby ensuring that the bone segment to be distracted obtained its blood supply via both the lingual and crestal side. The mental nerves were always identified on both sides.

Figure 2: Mondeal® vertical distractor for edentulous mandible.

Figure 1: Endo-distraction Implant ® according to Krenkel.

53


The EOD device was first fixated: the 12-hole base-plate (length 56 mm, thickness 2 mm) at the lower border with titanium screws (length 9 mm, diameter 1.2 mm); and the 6 hole upper plate (length 32 mm, thickness 2 mm) at the top of the residual mandible with 5 mm screws (diameter 1.2 mm). A horizontal osteotomy was performed in between the two plates, using a reciprocal saw. Care was taken to restrict the osteotomy to the interforaminal area. To facilitate mobilization of the upper segment, the distractor was temporarily removed. After remounting the distractor, the wound was closed in layers, taking care to keep the adjustment screw visible (Fig. 3). The IOD device was inserted in the middle of the symphyseal area. After drilling a hole in both the cranial and basal segments, the distraction rod was guided through the basal bone segment into the soft tissues of the sub-mandibular chin area. The upper segment was fixated to the upper part of the device, thus moving upwards when activating the rod by turning it to the left. After closing the wound, only the top of the device was visible (Fig. 4).

In both techniques, perioperative antibiotics were administered as well as chlorhexidine mouth washes. Because of the changing contour and the presence of the top of the distractor device in the oral cavity, the lower dentures could not be worn during the distraction period.

Figure 3: Extra-osseous distractor device after closure of the soft tissues with the adjustment nut visible.

54

After a 7-day latency period, activation of the distraction device was initiated. The EOD was activated at 0.5 mm a day; the IOD device was activated at from 0.25 mm at the beginning up to three to four times 0.25 mm a day. A consolidation period of 10–12 weeks followed the distraction period, after which the distractor was removed and in the same session the endosseous implants were installed. Four months later, prosthetic rehabilitation was performed: patients treated with an EOD received two per-mucosal implants to allow for a bar- or ball retained overdenture. In patients treated with an IOD, four implants were placed to support individual milled bars with dorsal elongations, onto which a removable bridge was positioned.

3-4 Lateral cephalometric tracingsFor each patient, lateral cephalometric radiographs were compared, taken both preoperatively and postoperatively, as at the end of the distraction period. By making tracings, measurements were performed using the Frankfurter horizontal plane as a reference. Perpendicularly, first an auxiliary line was constructed. Subsequently, another line, tangent to the top and the bottom of the alveolar process, was drawn at a right angle to this auxiliary line (Fig. 5). As such, the bone height at the mandibular symphysis could be measured using an electronic digital calliper (ETC industrial® ETC Europe).

To calculate the angle of the lingual movement of the upper segment, an extra auxiliary line running through the heart of the distractor device was drawn.

Figure 4: Intra-oral view of the Endo-distraction Implant ® according to Krenkel at the end of the distraction period.

55


The difference in angles, as measured before and after active distraction, served as an indication of the backward tilting of the upper segment (Fig. 6).

Figure 6: The angle between the position of the distractor device 1 day after placement and at the end of the distraction period.

Figure 5: Measurement of the residual bone height (RH) using the Frankfurter Horizontal Plane (FHP) as a reference. Arrow: forehead support with calibration points.

56

3-5 StatisticsStudent’s t-test for equality of means was used to elucidate differences in age, preoperative and postoperative bone height, increase in bone height and tilting between the IOD and the EOD group.

3-6 ResultsIn total, 88 edentulous patients with mandibular atrophy were treated by VDO. From 1998 to 2005, at the Department of Oral and Maxillofacial Surgery of the Hospital Gelderse Vallei (Ede, the Netherlands), 45 edentulous patients (4 males and 41 females, aged 36–77 years, mean age 63 years) underwent VDO of the edentulous mandible. In the same time period, at the Paracelsus Medical School, Salzburg, Austria, the edentulous mandibles of 43 patients (5 males and 38 females, aged 37–76 years, mean age 59 years) were distracted using an IOD.

No significant diversity between both groups, with respect to sex and age, was seen (Table 1).

Significant differences for both distraction devices were noted, regarding the preoperative and postoperative bone height, as well as the gained bone height (Fig. 7). There was a considerable difference between distractor type for backward tilting (Table 1). The average preoperative height of the EOD group was 11.9 mm (range 7.3–15.8 mm). This was substantially lower compared with the IOD group: mean height 18.6 mm (range 10.4–26.7 mm) (Table 2). Consequently, the total bone height, immediately after active distraction, showed an average of 17.9 mm (range 10.0–22.4 mm) for the EOD group and 27.8 mm (range 19.2–31.8) for the IOD group. The average gain in bone height was 6.0 mm (range 2.0–9.4 mm) for the EOD and 9.2 mm (range 2.0–19.1 mm) for the IOD group (Table 1).

All patients treated with an EOD, with the exception of one patient, showed a lingual movement of the upper segment caused by backward tilting of the device, with an angle ranging between 0° and 30°, with an average of 12.1°. Most of the patients treated with an IOD showed no or hardly any tilting of the device (mean tilting 3.0°, range 0–14°). Due to fracturing of the basal segment and the lower half of the distraction screw, two extreme values were encountered: tiltings of 30° and 20°, respectively.

Observed major complications for the EOD group were: 1) early fracture of the basal bone, occurring during osteotomy or shortly after placement of the device (2%); 2) late fracture of the basal bone, during active distraction or in the consolidation period (17%); and 3) sensory disturbances (28%).

Major complications in the IOD group consisted of: 1) anchorage loss of the cranial segment at an early stage with consequently minimal distraction (9%); and 2) anchorage loss later on with shrinkage of approximately 25%

57


Extra-osseousDevice

Intra-osseousDevice

N 45 43

Gender Male 4, Female 41 Male 5, Female 38

Age variation 36< >77 37< >76

Mean Standard deviation

Means Standard deviation

p-value

Mean age at operation

62,6 years 8,7 years 58,9 years 10,2 years 0.076

Bone height pre-operative

11,9 mm 2,1 mm 18,6 mm 4,5 mm 0,000*

Bone height post-operative

17,9 mm 2,4 mm 27,8 mm 3,6 mm 0,000*

Increase bone height

6.0 mm 1,7 mm 9,2 mm 4, 13 mm 0,000*

Tilting 12,1° 5,43° 3,0° 0,5° 0,000*

Table1: Represents number of patients, gender distribution, age variation, mean age at operation, bone height pre- and postoperative, the increase of bone height and the degree of backwards tilting. *P-values< 0.05 mm are statistically significant.

0

10

20

30

40

50

60

70

80

90

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43

Salzburg Age

Ede Age

Salzburg pre‐op bone height

Ede pre‐op bone height

Figure 7: Comparison of Salzburg and Ede patient groups in age and preoperative bone height.

58

of the already-gained bone height (9%). Only one fracture of the basal bone (2%) was observed. No sensory disturbances were encountered

3-7 DiscussionAugmentation of the atrophic edentulous mandible by distraction osteogenesis results in sufficient bone volume, to allow for installation of permucosal implants, and restoration of the diminished facial height. 9 In addition, this technique avoids donor-site morbidity and complications associated with transplanted bone blocks. 19 17 1 However, besides advantages, also restrictions and complications have been reported. 2 4 15 Although, with respect to age and sex, the IOD and EOD groups of patients were comparable, an obvious difference in the preoperative mandibular height was observed. This is explained by the difference in prosthetic concepts used in both groups. For the Dutch group, working with the EOD, the goal was to create sufficient bone volume to allow for the placement of only two implants with a minimal length of 12 mm. Onto these two implants, an implant–mucosa borne overdenture was constructed, thereby offering more comfort and chewing function. In aiming for a pure implant-supported construct, comprising individual gold bars on top of four implants with a length of at least 15 mm, the Austrian concept was quite different compared with the Dutch approach. To date, their aim was also to reconstruct physiological circumstances with a “normal” shaped vestibulum oris and plica circumlingualis. For that reason, patients with a relatively “high” residual ridge of 18 mm height on average, also underwent intra-osseous distraction.

In addition, using the Endo-Distraction Device, a minimum bone height of 5 mm of the transport bone fragment is necessary for adequate fixation of the hollow screw part, to avoid anchorage loss. Also, to guide the distraction rod optimally, sufficient bone height in the basal part of the mandible is needed. As such, for this IOD concept, a minimum vertical height of 10 mm is indicated.

In the group of patients with an EOD, the upper bone segment tends to incline lingually, due to the tension forces of mucoperiosteal tissue and stressed muscles. The mean degree of lingual tilting was 12.1°. Unexpectedly, for the intra-osseous device, the lingual tilting was only 3.0°. Although various authors mentioned backward tilting, no measurements were reported for this. An explanation of the high degree of backward tilting of the EOD may be, that there is some tolerance in the device itself, consisting of plates, body and spindle. This study shows that, whereas in the EOD group, the vector of distraction is rather unpredictable, 11 in the IOD group, a minimal tendency to tilting was observed, showing that the vector of distraction was relatively stable. Surprisingly, in a study published by Saulacic et al. in 2007, comparing the MODUS® EOD (Medartis, Basel, Switzerland) with the LEAD® IOD (Leibinger, Freiburg, Germany), the opposite was shown; more tilting was found in the IOD14. However, in 2008 Garcia et al. reported a modification for the LEAD® IOD, to allow for the distracting rod to be sunk into the hole and so avoid lingual tilting, 5 thereby resembling the concept of our Endo-Distraction Device.

59


In the EOD group, eight late fractures ware observed during the distraction and consolidation period (17%), while in the IOD group, only one fracture occurred. Also, for the Groningen Distraction Device® (Martin Medizin Technik, Tuttlingen, Germany) as IOD, out of 46 patients, only one fracture was reported. Although one can imagine that the osteosynthesis plate, as part of the EOD concept, reinforces the basal bone, 17 apparently, the opposite is the case; the multiple screws used to fixate the osteosynthesis plate indeed weaken the basal bone. At first glance, the low fracture rate in the present study for the IOD group may also be explained by the high preoperative residual bone height. However, also in the study using the Groningen Distraction Device® including only patients with a mandibular height between 5 and 9 mm, one patient had a fracture. 13

Sensory disturbances of the chin area after vertical distraction were only observed in the EOD group. This might be clarified by the fact that, although the extra-osseous devices are well miniaturized, screw fixation of the plates needs considerable deglovement of the soft tissues, thereby enlarging the operation area. Moreover, removal of the EOD devices again needs wide exploration of the same area, once again compromising the mental nerves. In contrast, placement, as well as removal, of the intra-osseous distraction device caused hardly any damage to the region, as also stated by others. 13

In the IOD group, anchorage loss occurred eight times: in four cases, in the first week after placement, therefore needing re-operation; in the other four cases, during the consolidation period. As a consequence, diminishing of the already achieved bone height was observed, although without affecting the implant placement. Anchorage loosening may be explained by a shortage of bone volume of the upper bone segment, either in height or in width, or by improper placement of the device in the upper bone segment.

Alveolar distractions of fully or partially edentulous regions are prone to a high rate of complications. 2 14 Only a few studies are available that focus on the fully edentulous mandible. Using an EOD for VDO in edentulous mandibles, Enislidis et al.2 reported 19 complications in nine VDO procedures (211%). They concluded, that the use of an EOD for VDO of edentulous mandibles is hazardous and doubted if there is a place for these devices for vertical alveolar distraction in edentulous patients in the future. With respect to the IOD, the results of Raghoebar et al. 13 corroborates our findings. Of the 46 distracted edentulous mandibles, one fractured. In three patients, backward tilting was noted, caused by the fact that the distraction screw was too long, thereby giving the patient the opportunity to play with it. Another four patients reported slightly disturbed sensitivity, although this could not be confirmed by objective testing.

In conclusion, patients with severe atrophic edentulous mandibles can be treated with distraction osteogenesis both by EODs as well IODs.

60

Within the limitations of this study, it can be stated, that EODs not only resulted in a significantly more fractures of the basal fragment, but also the risk of sensory disturbances, caused by the extensive deglovement of the chin area, was increased.

61


Reference

1 Clavero J, Lundgren S. Ramus or chin grafts for maxillary sinus inlay and local onlay augmentation: comparison of donor site morbidity and complications. Clin Implant Dent Relat Res. 2003: 5: 154-60.

2 Enislidis G, Fock N, Ewers R. Distraction osteogenesis with subperiosteal devices in edentulous mandibles. Br J Oral Maxillofac Surg. 2005: 43: 399-403.

3 Gaggl A, Schultes G, Karcher H. Distraction implants: a new operative technique for alveolar ridgeaugmentation. J Craniomaxillofac Surg 1999: 27: 214.

4 Garcia AG,Martin MS, Vila PG, Maceiras JL. Minor complications arising in alveolar distraction osteogenesis. J Oral Maxillofac Surg 2002: 60: 496-501.

5 García-García A, Peñarrocha-Diago M, Somoza-Martín M, Gándara-Vila P, Camacho F. Modified LEAD System distractor to prevent tilting during alveolar distraction in the mandibular symphyseal region. Br J Oral Maxillofac Surg 2008: 46: 141-3.

6 Günbay T, Koyuncu Bo, Akay MC, Sipahi A, Tekin U. Results and complications of alveolar distraction osteogenesis to enhance vertical bone height. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008: 105: 7-13.

7 Hidding J, Lazar F, Zöller JE. Knockenregenration des Unterkieferalveolarfortsatzes mit Hilfe der Vertikalen Kallusdistraction. Dtsch Zahnärztl Z 1999: 54: 51.

8 Krenkel C, Grunert I. The Endo-Distractor for preimplant mandibular regeneration. Rev Stomatol Chir Maxillofac 2009: 110: 17-26.

9 Krenkel C, Gross J, Brandtner C, Triessnig R, Singh D, Enzinger S Hakman E, Plenk H. Mono-Endo Distractor Krenkel® zur Regeneration der Alveolarsatzregion. Implantologie 2010:18(2):135-152.

10 Perdijk FBT, Van Strijen PJ. Augmentation of Severe Mandibular Atrophy by Vertical Distraction Osteogenesis. In: Samchukov M, Cope J, Cheraskin A, eds: Mandibular Distraction Osteogenesis. St Louis, MO Mosby, 2001: 433-437

11 Perdijk FB, Meijer GJ, Van Strijen PJ, Koole R. Effect of extraosseous devices designed for vertical distraction of extreme resorbed mandibles on backward rotation of upper bone segments. Br J Oral Maxillofac Surg 2009: 47: 31-6.

12 Raghoebar GM, Liem RS, Vissink A. Vertical distraction of the severely resorbed edentulous mandible: a clinical, histological and electron microscopic study of 10 treated cases. Clin Oral Implants Res 2002: 13: 558-65.

13 Raghoebar GM, Stellingsma K, Meijer HJ, Vissink A. Vertical distraction of the severely resorbed edentulous mandible: an assessment of treatment outcome. Int J Oral Maxillofac Implants 2008: 23: 299-307.

14 Saulacić N, Somosa Martín M, de Los Angeles Leon Camacho M, García García A. Complications in alveolar distraction osteogenesis: A clinical investigation. J Oral Maxillofac Surg 2007: 65: 267-74.

15 Saulacic N, Zix J, Iizuka T. Complication rates and associated factors in alveolar distraction osteogenesis: a comprehensive review. Int J Oral Maxillofac Surg 2009: 38: 210-7.

16 Silva FM, Cortez AL, Moreira RW, Mazzonetto R. Complications of intraoral donor site for bone grafting prior to implant placement. Implant Dent 2006: 15: 420-6.

17 Soares MM. Alveolar Distraction in the Class V and VI Edentulous Mandible. In Jensen OT. Ed : Alveolar distraction Osteogenesis. Chicago: Quintessence Publishing Co, Inc, 2002: 78-88.

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18 Uckan S, Oguz Y, Bayram B. Comparison of intraosseous and extraosseous alveolar distraction osteogenesis. J Oral Maxillofac Surg 2007: 65: 671-4.

19 Verhoeven JW, Ruijter J, Cune MS, Terlou M, Zoon M. Onlay grafts in combination with endosseous implants in severe mandibular atrophy: one year results of a prospective, quantitative radiological study.Clin Oral Implants Res 2000: 11: 583-94.

This chapter is an edited version of an article;Complications in Alveolar Distraction Osteogenesisof the Atrophic Mandible.

Int J Oral Maxillofac Surg. 2007 Oct;36(10):916-21.

F.B.T. PerdijkG.J. Meijer P.J. v. Strijen R. Koole

Complications in Alveolar Distraction Osteogenesis of the Atrophic Mandible4

64

De valkuil

65

Complications in A

lveolar Distraction O

steogenesis.Chapter 4

4-1 IntroductionAtrophy of the mandibular alveolar ridge often results in complaints, such as insufficient retention of the lower denture, pain by overloading the alveolar mucosa, 20 eat and speech difficulties, altered facial appearance and psychosocial problems. 22 Since dental implants have been shown a reliable basis for overdentures, reconstructive surgery aims to provide sufficient bone volume, to enable implant placement at the most optimal position from a prosthetic point of view. As an alternative for treatment of extreme atrophy of the edentulous mandible, the placement of short endosseous implants is suggested . However, the lack of vestibular and lingual sulcus in combination with limited attached mucosa in these cases, restrict this mode of treatment. Moreover, the consequence of short implants are an enhanced distance to the occlusal plane, inducing unfavourable biomechanical forces.

Therefore, various reconstructive and regenerative methods were introduced, to improve the bone height and the denture bearing area. Most of these surgical techniques include the application of cortico-cancellous bone blocks.

As an alternative to augmentation procedures with autologous bone grafts, in recent years advanced miniaturized distraction devices have been developed, to address the problem of the atrophied mandible. 5 9 12 Vertical distraction osteogenesis (VDO) creates vital bone in the space between the basal bone and the raised upper segment after a horizontal split osteotomy of the interforaminal mandible. During surgery, reflection of the mucoperiosteum is only limited to the labial surface. Implicating that both lingually, as at the top of the alveolar ridge, the mucosa remains attached to the underlying bone, preserving the blood supply to the upper bone segment. With this technique an increase of bone height and bone volume may be achieved to facilitate dental implant placement. Moreover, the surrounding soft tissues are distracted, thereby deepening the mandibular vestibular sulcus and broadening the zone of attached mucosa.

Till now, few authors address the topic of long term results and complications with alveolar VDO. 21 4 Only 2 reports are focussed on VDO in relation to the severe atrophied mandible. 7 15 Enislidis et al. (2005) conclude, that alveolar VDO is hazardous and doubtful, in contrast to Garcia et al. (2003), who conclude that VDO is an acceptable method with minor complications. 8 The aim of this study is to evaluate the complications associated with VDO of the severe atrophied mandible. An additional discussion is started to establish if alveolar VDO may be a good alternative to traditional augmentation procedures.

4-2 Material and methodsFrom 1998 to 2005, 45 edentulous patients (4 males and 41 females, aged 36 to 77 years, mean age 63 years) underwent alveolar VDO. Preoperatively, the mean bone height measured in the symphysis area, as measured on

66

lateral cephalometric radiographs, was 12.0 mm, varying from 7.3 to 15.8 mm.

All patients were treated with the Mondeal ® submucosal vertical distraction device (Mondeal Medical Systems GmbH, Tuttlingen, Germany). In total 99 Friadent (Friadent GmbH, Mannheim, Germany) dental implants were installed (12 IMZ®, 22 Frialit-II®, 65 Xive® ) with a length of 15mm. In 2 patients 2 ITI® implants (Institute Straumann AG, Switzerland) with a length of 14mm were inserted.

The selection criteria of patients include: good general physical and mental health, no drug and/or alcohol abuse, no smoking and no systemic diseases that could interfere with normal wound healing.

All procedures were approved by the Medical Ethical Committee of Northern Holland.

4-3 Surgical procedureInstallation of the distraction device was performed under general anaesthesia. One hour before surgery, 1 million units of phenyl penicillin were given intravenously, which was continued every 6 hours during the first 24 hours. Initially, the mandibular bone surface was exposed by a horizontal incision at the labial surface, followed by careful elevation of the mucoperiosteum to avoid injury to the mental nerves. In order to create an optimal overview, both foramina mentales were identified. Both at the top of the alveolar ridge as at the lingual site, the mucosa remained attached to the bone, thereby preserving the blood supply via the periosteum. Subsequently, the distractor device was fixated; the 12-hole base plate (length 56mm, thickness; 2 mm) at the lower border with titanium screws, (length 9 mm, diameter 1.2 mm) and the 6-hole upper plate (length 32mm, thickness; 2 mm) at the top of the residual mandible with 5 mm screws (diameter 1.2 mm ). In between both plates, a horizontal osteotomy was performed, using a reciprocal saw (Medicon® Instruments Tuttlingen, Germany). Care was taken to restrict the osteotomy to the interforaminal area. To facilitate mobilizing of the upper segment, the distractor was temporarily removed. After remounting the distractor, the wound was closed in layers, taking care to keep the adjustment nut visible (fig 1).

After a latency period of 1 week, the patients themselves activate the distractor by turning the adjustment nut with a rate of 0, 5 mm/day. After the desired bone height was gained, in order to consolidate the achieved bone volume, the distractor was kept in place for an additional period of 12 weeks. This implicates, that mandibular dentures could not be worn during this period. Patients were instructed for oral hygiene and soft diet. After this consolidation period of 12 weeks, the distractor was removed and biopsies were taken from both the upper and basal segment as also from the distracted bone. In the same session, 2 endosseous implants were

67

Complications in A



installed at the location of the former cuspids. After another 3 month, the implants were exposed and temporary abutments were placed, followed by the construction of a bar-retained overdenture.

4-4 Monitoring complicationsComplications were observed at four time periods: 1) intra-operatively, during installation of the distractor device, 2) between week 1-3, during the

Figure 1: Mondeal ® vertical distractor in situ at the start of distraction. The upper part is still in contact with the basal part.

Installationof

distractor

3 weeks 15 weeks1 week

Removal of distractor + placement of implants

0

End of VD

procedure

Start of VD

procedure

Consolidation period(12 wks)

Vertical Distraction (VD) period (0-2 wks)

Period afterimplant placement

Installationof

distractor

3 weeks 15 weeks1 week

Removal of distractor + placement of implants

0

End of VD

procedure

Start of VD

procedure

Consolidation period(12 wks)

Vertical Distraction (VD) period (0-2 wks)

Period afterimplant placement

Figure 2: Time table; after installation of the distractor, the vertical distraction (VD) procedure started after 1 week. When the optimal height was achieved, a 12 week period of consolidation was attended. At week 15, the distractor device was removed and subsequently, 2 end-osseous implants were inserted.

68

active vertical distraction (VDO) procedure, 3) between week 3-15, during the consolidation phase and 4) from week 15, after implant placement).

Intra-operative complications comprise fracturing of the osteotomy segments (‘early fracture’) and excessive bleeding. Complications during the VDO procedure varied from infection, skin perforation, mucosal dehiscence, to vector problems. Complications during the consolidation phase include fracture of the basal bone segment (‘late fracture’), persisting subjective sensory disturbances and the evolvement of a sagging chin. Complications after implant placement are focussed on loss of dental implants.

4-5 Radiographic procedurePanoramic and cephalometric radiographs were obtained preoperatively, immediate after the installation of the distractor device and at the end of the distraction period. Also, after implant placement, radiographs were taken and annually thereafter.

4-6 ResultsIntra-operative complications

‘Early fracture’ of the basal bone segment’

During the osteotomy in 1 (2%) patient with a vertical mandibular height of 13,6 mm, the basal segment fractured (fig. 3). Installation of an additional 2mm osteosynthesis plate (Mondeal Mini 2000 ®) was needed to stabilize this fracture. Excessive BleedingPostoperatively, no excessive bleeding was observed, although 2 patients (4%) showed haematoma in the floor of the mouth or at the chin region (fig.

Figure 3: Graphic showing the percentages of complications; implant failure (13%), sagging chin (13%), sensory disturbance (28%), dehiscence (8%), skin perforation (2%), infection (6%), bleeding/haematoma (4%), late fracture (17 %), early fracture (2%).

69

Complications in A



3). These patients had no anticoagulation medication or predisposition to bleeding.

Complications during the VDO procedure

InfectionDespite antibiotic prophylaxes, 3 patients (6%) developed post-operative infection (fig. 3). Therefore, local irrigation, additional oral hygiene instruction and administration of antibiotics were performed. In 1 patient, infection caused extensive loss of the new formed bone in the distraction gap.

Skin perforationOne patient (2%) suffered from a skin perforation at the chin region caused by the distractor device (fig. 3). Mucosal dehiscenceAfter installation of the distractor device the mucosa was carefully closed in layers. Nevertheless, in 4 patients (8%) dehiscence’s occurred. Improved local oral hygiene and chlorhexidine rinsing were indicated to stimulate secondary wound healing (fig. 3).

Vector problems

All patients showed a lingually orientated rotation of the upper bone segment.

Complications during the consolidation phase

‘Late fracture’ of the basal bone segment

During the consolidation period, in 8 patients (17%) the basal segment fractured (fig. 3). Their initial vertical height, as measured on the preoperative cephalometric radiographs, varied in 4 patients between 8-9 mm, in 1 patient between 9-10 mm, in 3 patients between 10-11 mm and in 1 patient between 15-16 mm. In total 6 patients with a mandibular height of less than 10mm were distracted, of which 50% suffered from a fractured mandible. Three patients heard a “sudden click” and suffered from a “stab of pain”. Five patients showed no clinical signs, although a mandible fracture was observed during radiographic surveillance. Clinically, in some cases at the lower border of the mandible a small step could be palpated, which could be radio-graphically confirmed. In 2 out of 8 cases, also the titanium basal plate (2 mm) was fractured (fig. 4a, b), resulting in dislocation of the lower border fragment.Both patients needed additional plate fixation after early removal of the (already activated) distractor. The other 6 patients suffered from minimum dislocation which healed uneventfully (fig 5a-c). It must be realized, that in these cases fixation of the fractured mandible was generated by the base plate of the distraction device.

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(a)

(b)

Figure 4: (a). The upper segment was already 8 mm lifted when a fracture occurred. (b) Another patient where proceeding distraction resulted in a fracture of the basal bone, the basal plate included.

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Fig. 5a.

Fig. 5b.

Figure 5: (a) After hearing a sudden click a OPT was made, revealing a late fracture without dislocation. (b).Situation after insertion of the implants.

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Sensory disturbances

Both during installation as removal of the distractor device, the mental nerves were identified. Despite avoiding nerve contact, solely degloving of the soft tissues in the chin area may cause sensory disturbances. Immediate after distractor installation, most patients perceived some slight sensory disturbance. This effect was amplified by the second deglovement, in order to remove the distractor. Recurrence of sensibility occurred in most of the patients, although 13 (28%) patients suffered from paraesthesia after 1 year (fig.3).

Sagging Chin:

In 6 patients (13%) a “sagging chin” was observed, implicating that, after performing a mucoperiosteal flap at the chin region, re-attachment of the musculi mentales does not always occur (fig. 3). In 3 patients, the chin ptosis was corrected, improving the exposure of the vermillion of the lower lip. By a submental approach the excess of skin and adipose tissue was removed, as described by Powers et al. 1996. 13

Complications after implant placement

Failure of the implant.

In 8 patients, 11 installed endosseous implants appeared not to be successful of which 9 implants failed within the first year (fig. 6). After re-implantation, in 3 patients again 1 implant was lost. In these cases, a third attempt was needed, to achieve a successful clinical result .

Figure 5: (c) After 1 year later; uneventful healing of the fracture and successful osseo-integration of the implants

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4-7 DiscussionIn 1 patient, a fracture of the lower mandible border was encountered, induced during the osteotomy. In this case, after performing the osteotomy with an oscillating saw, a chisel was used, to separate the remaining union between the osteotomized segments. After this event the osteotomy technique was adapted; exclusively the saw was used. Also the design of the bone cut was altered. Already in oncologic resection surgery it was known, that sharp edges between the horizontal and vertical bone cuts may lead to fractures. 25 Therefore it was decided to taper the bone cut in a gull wing fashion. 19 Since then no more ‘early’ fractures occurred.

The incidence of haemorrhage of the floor of the mouth in our study is comparative to the risk of haemorrhage, reported from other surgical procedures, such as osteotomies, fixating mandibular fractures, vestibuloplasties with concomitant lowering of the floor of the mouth, implantation in the interforaminal region, extraction of teeth, surgical removals of a ranula and biopsy procedures . In our study no major bleeding was observed, although it is emphasized, that perforation of the lingual cortical plate of the mandible with sharp instruments like a reciprocal saw may cause injury to the branches of the submental and sublingual arteries, with consequential haemorrhage of the floor of the mouth, ultimately resulting in airway obstruction. Haemorrhage may occur immediate after the osteotomy or at a later stage. Therefore, cautiously inspection of the floor of the mouth after the separation of the bone segments, combined with careful postoperative surveillance (fig. 7), is obligatory. 1

Figure 6: Kaplan-Meijer curve illustrating the loss of implants in relation to time.

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Infection rate associated with the application of external distraction devices in general is reported to be 5 % till 30%. 3 This complication in relation to intra-oral distraction devices is only mentioned sparsely. 18 Due to the fast invasion of new vessels into the distraction gap, it is hypothesized, that this area is more resistant to infection, compared to augmentation cases using avascular bone blocks. 23 Apparently, prophylactic administration of antibiotics, combined with good oral hygiene, appears to be sufficient to reduce the infection rate to an acceptable level. In 1 patient, extensive bone loss was observed at the distraction gap, frustrating implant instalment. Reconstruction, using an autologous bone graft, was needed, to allow implant placement.

The skin perforation in the chin area was caused by a distractor prototype, allowing a vertical gain in bone height of 15mm. Due to its huge dimension, extensive pressure was conducted in the vestibular sulcus. Since the introduction of a smaller distractor type, limiting the maximum distraction distance to 10mm, no more skin perforations were observed.

In total 4 mucosal dehiscence’s occurred. This complication may be prevented by making the incision deep in the vestibular mucosa. This type of incision also guarantees generation of soft tissue during distraction.

As reported by other authors, instead of vertical displacement of the upper segment, 11 also in our study a more lingually orientated rotational movement was observed. Nevertheless, after vertical distraction sufficient

Figure 7: Haematoma floor of the mouth, 1 day postoperative.

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volume of vital bone was present, to allow implant instalment.

Fracture of the basal bone segment during the distraction procedure or in the consolidation period was observed 8 times and may occur, due to the extreme fragility of the basal bone. Muscular tension forces and masticatory function are thought to be responsible for these fractures. Because 50% of all fractures occurred in mandibles with less bone height than 10 mm, one may conclude, that such extreme resorbed mandibles are a contraindication for VDO.

Despite careful exploration of the mental nerves, not only during installation of the distractor, but also during removal of the distractor device, deglovement of the soft tissues caused laceration of the sensible mental nerves, resulting in sensory disturbances (28%) even after 1 year. In literature various percentages are reported, concerning sensory disturbances caused by pre-prosthetic surgery and implant placement, varying from 10%-36%. 24 6

In 6 patients (13%) a “sagging chin” was observed. Patients with severe mandibular atrophy already show changes in facial appearances, due to loss of attachment of the facial muscles, that originate from the alveolar process and basal bone, resulting in chin ptosis; a deepened submental fold and lingual inclination of the lower lip. 2 Stripping of the remained muscular attachment, to expose the mental region, may aggravate this phenomenon. Wound closure after the first and second operation with tension sutures to lift and reinsert the mental muscle, may reduce the development of this dropping chin. If necessary submental skin correction is possible, to improve the facial appearance.

In our patients 89% of the primarily installed dental implants succeeded. This is in the same order (90%) compared to the study of Enislidis et al. 7 who treated a group of 37 patients with VDO. Similar survival rates (88%) were reported for implants installed after an augmentation procedure with bone grafts.14 10 16 Also the alternative of installing 2 or 4 short implants in patients with extreme resorbed mandibles resulted in success percentages varying from 88 - 94 % after 5 years (Stellingsma et al., 2000). 17

4-8 ConclusionPatients with severe mandibular atrophy treated either with conventional augmentation techniques or with VDO are related to various complications. Most complications occur in the first year. Compared to other augmentations techniques, the complication rate in VDO is rather high; 66% of all patients suffered from one or more complication, varying from mucosa dehiscence, implant loss, to fracture of the mandible. Therefore, it must be stressed, that VDO may not be the first treatment of choice in correcting vertical bone height of the atrophied mandible. Moreover, extreme atrophied mandibles, with a preoperatively measured vertical bone height of less than 10mm, must even be considered as a contraindication for this method.

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Reference

1 Bruggencate CM ten, Krekeler G, Kraaijenhage HA, Foitzik C, Oosterbeek HS. Hemorrhage of the floor of the mouth resulting from lingual perforation during implant placement: a clinical report. Int J Oral Maxillofac Implants 1993: 8: 329-334.

2 Cawood JI, Howell RA. Reconstructive preprosthetic surgery .I. Anatomical considerations. Int J Oral Maxillofac. Surg. 1991: 20: 75-82.

3 Cherkash AM, Samchukov ML. Potential Mistakes and Complications During Distraction Osteogenesis. In: Samchukov ML, Cope JB, Cherkashin AM. ed.: Craniofacial Distraction Osteogenesis, St Louis, MO Mosby 2001: 583-594.

4 Chiapasco M, Consolo U, Bianchi A, Ronchi P. Alveolar Distraction Osteogenesis for the Correction of Vertically Deficient Edentulous Ridges: A Multicenter Prospective Study on Humans. Int J Oral Maxillofac Implants 2004: 19: 399-407.

5 Chin M, Toth BA. Distraction osteogenesis in maxillofacial surgery using internal devices: review of five cases. J. Oral Maxillofac. Surg. 1996: 54: 45-53.

6 Ellies LG, Hawker PB. The prevalence of altered sensation associated with implant surgery. Int J Oral Maxillofac Implants. 1993: 8(6): 674-9.


8 Garcia AG, Martin MS, Vila PG, Maceiras JL. Minor complications arising in alveolar distraction osteogenesis. J Oral Maxillofac Surg 2002: 60: 496-501.

9 Hidding J, Lazar F, Zöller JE. Vertical Distraction of the alveolar Process:. A New Technique for Reconstructing the Alveolar Ridge. In Samchukov ML, Cope JB, Cherkashin AM. ed.: Craniofacial Distraction Osteogenesis. St Louis: MO Mosby 2001: 393-400.

10 Meij EH van der, Blankestijn J, Berns RM, Bun RJ, Jovanovic A, Onland JM, Schoen J. The combined use of two endosteal implants and iliac crest onlay grafts in the severely atrophic mandible by a modified surgical approach. Int J Oral Maxillofac Surg. 2005: 34(2):152-7

11 Perdijk FBT, Meijer GJ, Van Strijen PJ, Koole R. The use of vertical distraction osteogenesis of the severe atrophied mandible: A retrospective study on cephalometric tracings. Submitted.

12 Perdijk FBT, V Strijen PJ, Correction of severe mandibular atrophy by means of distraction osteogenesis. 2nd International Congress on Cranial and Facial Bone Distraction Processes. Monduzzi Editore. 1999: 157-161.

13 Powers MP, Bosker H. Functinal and Cosmetic Reconstruction of the Facial Lower Third Associated With Placement of the Transmandibular Implant System . J Oral Maxillofac Surg 1996 : 54: 934-942.

14 Schliephake H, Neukam FW, Wichmann M. Survival Analysis of Endosseous Implants in Bone Grafts Used for the Treatment of Severe Alveolar Ridge Atrophy. J Oral Maxillofac Surg.1997: 55: 1227-1233.

15 Soares MM, Guerra F, Duarte P, Correa C, Maluf P. Increase of the Edentulous Mandibular Alveolar Ridge with Distraction Osteogenesis. 4th International Congress on Cranial and Facial Bone Distraction Processes. Monduzzi Editore. 2003: 87-92.

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16 Stellingsma K, Raghoebar GM, Meijer HJ, Stegenga B. The extremely resorbed mandible: a comparative prospective study of 2-year results with 3 treatment strategies. Int J Oral Maxillofac Implants. 2004: 19(4): 563-77.

17 Stellingsma C, Meijer HJ, Raghoebar GM.Use of short endosseous implants and an overdenture in the extremely resorbed mandible: a five-year retrospective study. J Oral Maxillofac Surg. 2000;58:382-7; discussion 387-8.

18 Strijen PJ van. Breuning KH, Becking AG, Perdijk FBT, Tuinzing DB. Complications in Bilateral Mandibular Disraction Osteogenesis using Internal Devices. Oral Surg, Oral Med. Oral Path. Oral Rad. and Endodontics. 2003: 96(4): 392-397.

19 Stucki-McCormick SU, Moses JJ. Vector and Stabilisation During Alveolar Lengthening by Distraction Osteogenesis. In: Jensen OT. (ed) Alveolar Distraction osteogenesis. Quintessence Publishing Co, Inc. 2002: 69-76.

20 Tallgren A. The continuing resorption of the residual alveolar ridge in complete denture wearers: a mixed longitudinal study covering 25 years. J Prosthet Dent 1972: 27: 120.

21 Uckan S, Haydar SG, Dolanmaz D. Alveolar distraction: Analysis of 10 cases. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002: 94: 561-565.

22 Waas MAJ van. The influence of clinical variables on patient satisfaction with complete dentures. J Prosthet Dent 1990: 63: 307-310.

23 Walker D. Buried bidirectional telescopic mandibular distraction. . In: Samchukov ML, Cope JB, Cherkashin AM. ed.: Craniofacial Distraction Osteogenesis, St Louis, MO Mosby 2001: 313-322.

24 Wismeijer D, van Waas MA, Vermeeren JI, Kalk W. Patients perception of sensory disturbances of the mental nerve before and after implant surgery: a prospective study of 110 patients. Br J Oral Maxillofac Surg. 1997 Aug: 35(4): 254-9.

25 Wittkampf ARM, Witkampf FJM. Prevention of mandibular fractures by using constructional design principles: part I. Int J Oral Maxillofac Surg 1995: 24: 306.

This chapter is an edited version of an article;Effect of extra-osseous devices designed for vertical distraction of extreme resorbed mandibles onbackward rotation of upper bone segments

Br J Oral Maxillofac Surg. 2009 Jan;47(1):31-6

Frits B.T. Perdijk Gert J. MeijerPeter J. van StrijenRon Koole

Effect of extra-osseous devices designed for vertical distraction of extreme resorbed mandibles on backward rotation of upper bone segments5

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Chapter 5Extra-osseous distractor devices and backw

ard rotation of upper bone segments.

5-1 IntroductionThe edentulous patient with a resorbed mandible (Cawood V-VI) 1 often have reduced retention and instability of the lower denture. 2 As well as impaired chewing, the diminished vertical height of the alveolar process results in loss of vertical dimension of the face and poor facial aesthetics. 3 Rehabilitation of the atrophied edentulous mandible has therefore been a challenge for some time. Various augmentation techniques have been proposed to create more bone height, such as the visor osteotomy 4, the sandwich osteotomy 5

6 7 8 or onlay grafts. 9 These all use bone grafts, introducing the risk of donor site morbidity. Resorption of the grafted bone is also possible.

As an alternative, alveolar vertical distraction osteogenesis (VDO) has been suggested, by which a horizontal split osteotomy of the anterior mandible is made between the mental foramina, creating a basal- and upper bone segment. Subsequently, with a special distractor, the upper segment can be lifted, thereby allowing the haematoma, that encircles the cut bone segments, to create bone. As tension is applied to the granulation tissue of the gap, the collagen meshwork becomes oriented in the direction of tension and the formation of woven bone follows this collagen scaffold. 10 11 The critical, mechanical and biological factors that regulate bone formation in the distraction gap include: preservation of periosteum, a delay or latency period after osteotomy before distraction, stable fixation to eliminate undesirable micro motion, slow distraction with small but daily steps and a consolidation period after the completion of distraction. 12 13

Recently, a systematic review on the subject found 128 articles published between January 1996 and December 2006 14. Although many studies have been published , only a few articles concern VDO for atrophy of the edentulous mandible.

There is an abnormal interalveolar relation between mandible and maxilla in patients with alveolar atrophy; this results in apparent projection of the jaw and reduced facial height. The alveolar crest must be reconstructed in the right direction.

In alveolar distraction, because of the tension forces of muco-periostal tissue and muscle power, the bone segment tends to incline lingually, making rigid control of the bone segments difficult. To solve this problem multi-directional distractor devices were developed. The difference in the amount of bone gain vertically observed between uni-directional and bi-directional devices was not significant. 15 In both methods there was also a bone deficit at the anterior surface of the alveolar ridge, showing a typical inclination of the long axis of the bone. 16

The aim of this study was to calculate the gain in bone height and to monitor the amount of lingual tipping of the distracted upper segment, using a extra-osseous unidirectional distraction device (Mondeal®).

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5-2 Patients and MethodThirty-four patients were enrolled and treated by VDO in the period between 1998 and 2005 at the Hospital Gelderse Vallei, Ede, The Netherlands. The mean follow-up period was 3 years( range 1 to 7).

Patients were included, if they had a severely resorbed edentulous mandible (Cawood V-VI); poor retention and instability of the lower denture; good general physical and mental health; no drug or alcohol misuse; did not smoke and no systemic diseases, that could interfere with normal wound healing.All procedures were approved by the Medical Ethical Committee of Northern Holland.

Surgical technique

The surgical procedure is explained in Chapter 4-3

Cephalometric tracings.

Cephalometric radiographs were taken preoperatively, immediate after installation of the distractor device; at the end of the active distraction period (1-2 weeks), before placement of implants, after a consolidation period of 12 weeks and then annually thereafter.

Figure 1: Measurement of the height of the mandibular bone using the mandibular plane as a reference. Arrow= forehead support with calibration points.

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Lateral cephalometric radiographs not only record height and width, but also show the backwards inclination of the alveolar ridge in the symphysiseal area. We made measurements using the mandibular plane as a reference, that is, the line drawn at a tangent to the posterior portion of the lower border of the mandible, stretching from point Gonion to the symphysis curve (point Menton). An auxiliary line was constructed perpendicularly and then another line tangent to the top of the alveolar process was drawn in a right angle to the auxiliary line. All cephalometric radiographs were superimposed, using the sella and nasion as references. It was calibrated by using the marks on the forehead positioner, that indicated a distance of 10mm (Fig. 1). Subsequently, measurements of bony height were made with an electronic digital calliper (ETC industrial ®). The angle of the lingual movement of the upper segment was calculated on the day, that the distraction device was installed and compared with the angle, that was measured at the end of the distraction period. (Fig. 2).

Statistics

The hypothesis was tested, using the analysis of variance for regression (ANOVA) that in with a low initial mandibular height the risk for backwards tilting of the distracted upper segment was increased.

Figure 2: The angle between the position of the distractor device one day after installation and at the end of the distraction period.

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5-3 ResultsThe average pre-operative height was 12.5 mm (range 7.3 - 15.8). The mean total bone height immediately after active distraction, was 18.5 mm ( range 13.9 to 22.4). So the mean gain was 6.1 mm ( range 3.3 to 8.5).With the exception of one patient, all had a lingual-movement of the upper segment, through backwards tilting of the distractor device, with an angle ranging between 0- 30 degrees (mean 12). The degree of lingually tipping was not related to the pre-operative bone height (p=0,06; Fig.3). As a result of the lingual tipping, all patients had a thinning of the labial cortex of the distracted area, resulting in a slightly concave shape of the bone (Fig.4).

Figure 3: There is no significant relation between the rotation angle of the distraction device and preoperative bone-height (n=34; p=0.06)

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Figure 4: Concave shape of the distracted bone.

5-4 DiscussionTo create a satisfying result, the denture should have sufficient retention and stability. To fulfil this, endosseous implants are used. To allow placement of implants, a stable basis of bone tissue is needed. Improvement of the configuration of the atrophic alveolar ridge can be realised by augmentation procedures, using autogenous bone onlay grafts, guided bone regeneration or application of alloplastic material. The use of only short implants to support an overdenture is also recommended 18. However, the lack of vestibular and lingual sulcus in combination with limited attached mucosa in these cases, makes this mode of treatment useless. The consequence of short implants is an increased distance to the occlusal plane, inducing unfavourable biomechanical forces. Complications such as fracture and osteomyelitis have been described by several authors. 19 20 Considering the age of the patient and the need to reconstruct the alveolar crest, the choice of treatment is clear. As an alternative to augmentation procedures with an autologous bone graft, in recent years advanced miniaturized distraction devices have been developed, to restore the alveolar ridge using osteodistraction.

Although, the distraction device aims to lift the superior segment only in a vertical position, the postoperative radiographs shows, that there is also a backward rotation of the upper segment. Previous authors have suggested, 21 that the pull of the mylohyoid and tongue muscles in a lingual direction, together with the tension of the periosteum affect the vector of distraction. The extreme value of a 30 degree backwards rotation in one patient may be explained by the co-occurrence of a fracture of the thin basal bone segment. We could not prove, that the magnitude of backward tilt was related to the pre-operative bone height (p=0,055; Fig.3), although there seems to be a strong tendency.

86

In the diagram of the symphyseal area of the atrophic mandible (Fig.5), squares A and B indicate the original bony height (h). After the horizontal osteotomy ( line E), the upper segment B is expected to be lifted into position B1. In reality, the distraction device rotates lingually with a mean of 12 degrees and transports bone segment B into position B2, thereby reducing the maximum achievable height from 100% to 97% (cosinus angle 12 degree is 0, 97). Point X, the favourable place for the permucosal implant, therefore moves to point XX. If the width of the upper segment is also taken into account (for example 10 mm), an extra reduction in height of another 1 mm is added (1/2 x 10 mm x sinus 12 degree = 1 mm) (d). The backward dislocation of point X to XX results in a lingual displacement of about 68 % ( a + c = b.sin 12 + e. cos 12) and a reduction of the vertical height of about 87% (f – d = b cos 12 – e sin 12 ).

As a consequence of the backward tipping of the upper bone segment, also the distraction gap (C) between A and B2 is tilted backwards, with the consequence of a bony deficit at the anterior surface of the alveolar ridge, as shown clinically and radiographically (three- dimensional scan made, just before removal of the distractor and instalment of dental implants; fig. 6).

Vector control of alveolar VDO has been described in cases of partial edentulism, where additional splints, wires or elastic bands, fixed on the remaining teeth, could interfere with the direction of the distractor device . In complete edentulous patients there is no possibility to control the arm of the distraction device. 23

5-5 ConclusionsIn atrophic mandibles, vertical distraction indeed results in a vertical lift of the upper segment. However, also a rotational movement in lingual direction was observed, varying between 0 and 30 degrees, with a mean of 12 degrees, resulting in a reduction of the vertical height between 0 and 3.9 millimetre, with a mean of 1.3 mm.

VDO is a useful tool, to reconstruct the bone height of atrophic alveolar mandibular ridges, in order to place dental implants, to improve the retention of overdentures and to restore facial harmony. Although VDO provides extra volume of vital bone, to ensure installation of longer implants, the direction of the distracted bone is less predictable as some authors may suggest. 24 25

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A and B: Original bone of the symphysis with bone height h.E: Line of osteotomy.C: Distraction callus(blue area).B1: Desired position of upper bone segment.B2: Position of the upper bone segment in case of a 12 degree backward Rotation. D: Position of the distractor device after placement. D1: Position of the distractor device after active distraction in case of a 12 degree backward rotation. f-d: Achieved bone height in case of 12 degree rotation of the distractor device.X: Ideal position in case of zero rotation.XX: Expected position for implant installation in case of 12 degree rotation.a+c: Backwards displacement of implant location in case of 12 degree rotation.abf, cde: Rectangular triangles with one angle of 12 degree.r-s, t-u: Anterior and posterior concave border of the distraction callus.

Figure 5: Schematic drawing of the symphysis area of the atrophic mandible with vertical distraction device. Mean rotation of the device of 12 degrees.

88

Figure 6: Three-dimensional picture at the end of the consolidation period of 12 weeks. Backward tilting of the distractor resulted in slight lingual movement of the upper bony segment. Distraction gap with newly-formed bone and the concave anterior border of the callus.

89



Reference

1 Cawood JI, Howell RA. A classification of the edentulous jaws. Int J Oral Maxillofac Surg 1988; 17:232- 236

2 Tallgren A: The continuing resorption of the residual alveolar ridge in complete denture wearers: amixed longitudinal study covering 25 years. J Prosthet Dent, 1972; 27: 120,

3 Hidding J, Lazar F, Zöller JE: Vertical Distraction of the alveolar Process: A New Technique for Reconstructing the Alveolar Ridge. In Samchukov ML, Cope JB, Cherkashin AM, editors: Craniofacial Distraction Osteogenesis, St Louis, MO Mosby, 2001; 393-400

4 Härle F. Visor osteotomy to increase the absolute height of the atrophic mandible. J Maxillofacial Surg 1975;3:257

5 Hofer O, Mehnert H. Eine neue methode zur Rekonstruction des Alveolarkamms. Dtsch Zahn Mund Kieferheilk 1964; 41:25

6 Schettler D. Holterman W. Clinical and experimental results of a sandwich-technique for mandibular ridge augmentation. J Maxillofac Surg 1977; 5: 199.

7 Stoelinga PJW,Tideman H, Berger JS, Koomen HA de. Interpositional bone graft augmentation of the atrofic mandible: A preliminary report. J Oral Surg 1978; 36:30.

8 Stoelinga PJW, Koomen HA de, Tideman H, Huybers AJM.: A reappraisal of the interposed bone graft augmentation of the atrophic mandible. J Maxillofac Surg 1983; 11:107

9 van der Meij EH, Blankestijn J, Berns RM, Bun RJ, Jovanovic A, Onland JM, Schoen J.The combined use of two endosteal implants and iliac crest onlay grafts in the severely atrophic mandible by a modified surgical approach. Int J Oral Maxillofac Surg. 2005;34(2):152-7

10 Ilizarov, G. A. “The tension-stress effect on the genesis and growth of tissues: Part II. The Influence of the rate and frequency of distraction.” Clin.Orthop 239 (1989); 263-85.

11 Aronson, J. “Preliminary studies of mineralization during distraction osteogenesis.” Clin.Orthop 250 (1990); 43-49

12 Amir LR, Becking AG, Jovanovic A, Perdijk FB, Everts V, Bronckers AL.Vertical distraction osteogenesis in the human mandible: a prospective morphometric study. Clin Oral Implants Res 2006 Aug;17(4):417-25.

13 Amir LR, Becking AG, Jovanovic A, Perdijk FB, Everts V, Bronckers AL. Formation of new bone during vertical distraction osteogenesis of the human mandible is related to the presence of blood vessels. Clin Oral Implants Res 2006 Aug;17(4):410-6.

14 Saulacic N, Iizuka T, Martin MS, Garcia AG. Alveolar distraction osteogenesis: a systematic review. Int J Oral Maxillofac Surg 2007 Sep 4; [Epub ahead of print]

15 Schleier P, Wolf C, Siebert H, Shafer D, Freilich M, Berndt A, Schumann D. Treatment options in distraction osteogenesis therapy using a new bidirectional distractor system. Int J Oral Maxillofac Implants 2007 May-Jun;22(3):408-16.

16 Iizuka T, Hallermann W, Seto I, Smolka W, Smolka K, Bosshardt DD. Bi-directional distraction osteogenesis of the alveolar bone using an extraosseous device. Clin Oral Implants Res 2005; 16(6):700-7.

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17 Habets LLMH. Atrofie van de mandibula en metabool botverlies. 1988 (dissertation) Amsterdam, The Netherlands: University of Amsterdam.

18 Stellingsma C, Meijer HJ, Raghoebar GM. Use of short endosseous implants and an overdenture in the extremely resorbed mandible: a five-year retrospective study. J Oral Maxillofac Surg 2000;58:382-7; discussion 387-8.

19 Mason ME, Triplett RG, Van Sickels JE, Parel SM. Mandibular fractures through endosseous cylinder implants: report of cases and review. J Oral Maxillofac Surg 1990 Mar;48(3):311-7. Review.

20 Tolman DE, Keller EE. Management of mandibular fractures in patients with endosseous implants.Int J Oral Maxillofac Implants 1991 Winter;6(4):427-36

21 Stucki-McCormick SU. Moses JJ. Vector and Stabilisation During Alveolar Lengthening by Distraction Osteogenesis. In: Jensen OT. (ed) Alveolar Distraction osteogenesis. Quintessence Publishing Co, Inc,IL. 2002; 69-76.

22 Herford AS, Audia F. Maintaining vector control during alveolar distraction osteogenesis: a technical note.Int J Oral Maxillofac Implants 2004 Sep-Oct;19(5):758-62.

21 Bianchi A,Degidi M,Gentile L,Piatelli A,Cocchi R. Distraction Osteogenesis of the Alveolar Process: the “New”Preprosthetic Surgery In: Diner PA, Vazquez MP(eds) 3rd International Congress on Cranial and Facial Bone Distraction Processes [14-16 June 2001,Paris,France]. Bologna, Italy:Monduzzi,2001.

22 Clarizio LF. Vertical Alveolar Distraction Versus Bone Grafting for Implant Cases: The Clinical Issues. In Jensen OT (ed) Alveolar Distraction Osteogenesis Quintessence Publishing Co, Inc,IL. 2002; 59-67

23 Chiapasco M, Consolo U, Bianchi A, Ronchi P. Alveolar Distraction Osteogenesis for the Correction of Vertically Deficient Edentulous Ridges: A Multicenter Prospective Study on Humans. Int J Oral Maxillofac Implants 2004; 19: 399-407.

This chapter is an edited version of the manuscript;The lower border augmentation technique to allow implant placement after a bilateral mandibular fracture as a complication following vertical distraction osteogenesis;a case report

submitted to the Int J Oral Maxillofac Surg

F.B.T. PerdijkG.J. Meijer A. Soehardi R. Koole

The lower border augmentation technique to allow implant placement after a bilateral mandibular fracture as a complication following vertical distraction osteogenesis; a case report6

The lower border augm

entation technique.Chapter 6

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6-1 IntroductionEdentulous patients with an extremely resorbed mandible (Cawood V-VI) 1 often have reduced retention and instability of the lower dentures. 2 Besides impaired masticatory function, the diminished vertical height of the alveolar process results in loss of vertical dimension of the face and poor facial aesthetics 3. Improvement of denture retention can be obtained by installation of endosseous implants. In extreme cases jaw atrophy even impedes implant placement. To create more bone height, various augmentation techniques have been proposed using autologous bone as well as bone substitutes. Vertical distraction osteogenesis (VDO) can also be performed. However, VDO of fully or partially edentulous regions is prone to a high rate of complications, 4 5 6 7 8 9 such as mandibular fracturing. To deal with a fracture of a extremely edentulous mandible and at the same time allow implant placement at a second stage, application of a bone graft onto the lower body of the mandible, that is restricted to the interforaminal mandibular region ( i.e. sub-mentally), is advocated.

6-2 Case reportA 65-year-old male required dental implants, to improve the retention and stability of his denture. Intraorally, a diminished alveolar ridge was visible as a heightening of both the floor of the mouth and the buccal sulcus. Panoramic, lateral cephalometric radiograph and even cone beam computed tomography were performed, to determine the available residual bone volume of the mandible. The bone height in the symphyseal area was measured 8 mm. (Fig. 1a) It was decided to augment the mandible by VDO, using an intra-osseous device (IOD) (Endo-Distraction Krenkel®, Mondeal®, Tuttlingen, Germany) prior to the placement of two endosseous implants.

ab

b a

Figure 1a: before the VDO procedure, 1b: after the lower border augmentation and implant installation

b a

Figure 3a: frontal view showing the submental approach elucidating the iliac crista graft (b) positioned at the lower mandibular border ( hit )(white arrow)

a

b

Figure 2 showing the osteosynthesis plates around the first fracture (black arrow) and the second fracture (white arrow).

Figure 4: lateral view after lower border augmentation and implant installation. The arrow points to the transition of ‘old’ bone to ‘new’ bone: a: 3‐dimensional impression of the CBCT (b)


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Surgical procedure

The surgical technique described by Krenkel et al, 10 was done under general anaesthesia. First, a muco-periostal flap was reflected on only the vestibular side, leaving the periosteum in place on the alveolar crest. After identification of both mental nerves, a horizontal osteotomy was performed, using a reciprocal saw. The IOD was inserted in the middle of the symphyseal area. After drilling a hole in both the cranial and basal segments, a distraction rod was guided through the basal bone segment into the soft tissues of the sub-mandibular chin area. The upper segment was fixated to the upper part of the device, thus moving upwards, when activating the rod by turning it. After wound closure, only the top of the device was visible. During and after completion of surgery, the distractor device remained in the correct position and no complications were encountered.

One day post operatively, dislocation of the distractor device was observed. On the panoramic radiograph a fracture at the right side of the corpus of the mandible was visible. The distractor device was surgically removed and the fractured mandible fixated with a six hole osteosynthesis plate (Mondeal 2000 ®; Mondeal, Tuttlingen, Germany) and two additional lack screws. Over the next fortnight, healing was complicated by elucidating pain, swelling and dislocation of the lack screws. Surgery was once again performed, to stabilize a new fracture with additional plate osteosynthesis; this time at the left side of the mandibular body (Fig. 2). During the following 2 months healing seemed to be disturbed; prolonged administration of clindamycin was necessary, because of continuous infection, causing pain and discharge of pus. Computer tomography showed sequestration of bone segments, indicative of osteomyelitis. Three month after the first operation all osteosynthesis material was removed and sequesterectomy was performed. Stabilisation of the mandible was achieved by an acrylic splint, fixated by peri-mandibular wiring. Antibacterial therapy was continued

ab

b a


b a


a

b



Figure 2: showing the osteosynthesis plates around the first fracture (left arrow) and the second fracture (right arrow).



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for several weeks. Two months later the acrylic splint was removed and a month after that, callus formation was already radiographically visible. Eight month after the VDO-procedure the patient underwent a lower border onlay grafting, limited to the symphyseal area, in preparation for implant insertion, as proposed by Soehardi et al. 11 First, a cortico-cancellous bone graft of approximately 3 x 3 cm was harvested from the anterior iliac crest (Fig. 3b). Subsequently, via a submental approach, the lower border was exposed over an area of about 3 cm. Then, the graft was modeled, as to fit the contour of the exposed bone and fixated trans-orally by two screws.

Healing after surgery was uneventful and 5 months later two implants (Brånemark System®, Mk III Groovy, Nobel Biocare, Sweden) were installed. ( Fig. 1b, 4) Prosthetic follow up was realized by locator abutments and overdenture. Four years after the first operation, the patient has good masticatory function with a stable denture with good retention. Panoramic radiographs show good continuous bone in the operated area. Bilaterally some numbness of the lower lip and chin area was noted.

ab

b a


b a


a

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Figure 3a: frontal view showing the submental approach elucidating the iliac crista graft (b) positioned at the lower mandibular border .

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6-3 DiscussionAtrophic mandible fractures are commonly seen in maxillofacial practice. These fractures may occur after trauma, after pre-implant surgery such as VDO, during or after implant placement 12 13 14 or spontaneously. No consensus has been reached, regarding the best treatment for repair of fractures of the severely atrophic mandible (<10 mm vertical height). The most complete Cochrane review of the published data could not substantiate a single best practice recommendation for treating these fractures. 15 The treatment of a fracture in an atrophic mandible is always a challenge, because of the diminished central blood supply, the depressed vitality of the bone and the dependence on the periosteal blood supply. The basic principles in fracture treatment are reduction and immobilization of the fractured site. 14 Methods of treatment of edentulous mandibular fractures vary between closed reduction, rigid fixation using osteosynthesis plates and application of bone grafts. In a survey of 157 fractured edentulous mandibles, fracture treatment was uneventful in 52% of the patients, but considerable complications, such as osteomyelitis and non- union, occurred in 48%. 12

Together with the insertion of implants in already fractured edentulous mandibles extra risk factors for renewed complications are introduced. With the lower border grafting technique a substantial augmentation of the mandibular height can be achieved, without reopening the already scarred intra oral tissues. 16 17 18 19 20 21 22 23 24 25 26

In the present case reinforcement of the mandible and improvement of denture retention were successfully achieved, solely by using the lower border grafting technique via an extra-oral sub-mental approach. Therefore, the lower border augmentation technique can be a valuable treatment option in compromised atrophic mandible patients, demanding an implant retained overdenture.

ab

b a


b a


a

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Figure 4a,b: lateral view after lower border augmentation and implant installation. The arrow points to the transition of ‘old’ bone to ‘new’ bone: 3-dimensional impression of the CBCT (b)



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Reference

1 Cawood JI, Howell RA. A classification of the edentulous jaws. Int J Oral Maxillofac Surg 1988; 17:232-236

2 Tallgren A: The continuing resorption of the residual alveolar ridge in complete denture wearers: a mixed longitudinal study covering 25 years, J Prosthet Dent 27; 120, 1972

3 Hidding J, Lazar F, Zöller JE: Vertical Distraction of the alveolar Process: A New Technique for Reconstructing the Alveolar Ridge. In Samchukov ML, Cope JB, Cherkashin AM, editors: Craniofacial Distraction Osteogenesis, St Louis, MO Mosby 2001; 393-400


5 Garcia AG,Martin MS, Vila PG, Maceiras JL. Minor complications arising in alveolar distraction osteogenesis. J Oral Maxillofac Surg 2002: 60: 496-501.

6 Günbay T, Koyuncu BO, Akay MC, Sipahi A, Tekin U. Results and complications of alveolar distraction osteogenesis to enhance vertical bone height. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2008: 105: 7-13.

7 Saulacic N, Zix J, Iizuka T. Complication rates and associated factors in alveolar distraction osteogenesis: a comprehensive review. Int J Oral Maxillofac Surg 2009: 38: 210-7.

8 Saulacić N, Somosa Martín M, de Los Angeles Leon Camacho M, García García A. Complications in alveolar distraction osteogenesis: A clinical investigation. J Oral Maxillofac Surg 2007: 65: 267-74.

9 Perdijk FB, Meijer GJ, Strijen PJ, Koole R. Complications in alveolar distraction osteogenesis of the atrophic mandible. Int J Oral Maxillofac Surg. 2007 Oct;36(10):916-21

10 Krenkel C, Grunert I. The Endo-Distractor for preimplant mandibular regeneration. Rev Stomatol Chir Maxillofac. 2009 Feb;110(1):17-26.

11 Soehardi A., Meijer G.J., Bergé, S.J., Stoelinga, P.J.W. Lower border bone onlays to augment the severely atrophic (Class VI) mandible in preparation for implants: a preliminary report. Int J Maxillofac Surg (accepted).

12 Soehardi A, Meijer GJ, Manders R, Stoelinga PJ. An inventory of mandibular fractures associated with implants in atrophic edentulous mandibles: a survey of Dutch oral and maxillofacial surgeons. Int J Oral Maxillofac Implants. 2011 Sep-Oct;26(5):1087-93

13 Oh WS, Roumanas ED, Beumer J 3rd. Mandibular fracture in conjunction with bicortical penetration, using wide-diameter endosseous dental implants. J Prosthodont. 2010 Dec;19(8):625-9

14 Chrcanovic BR, Custódio AL. Mandibular fractures associated with endosteal implants. Oral Maxillofac Surg. 2009 Dec;13(4):231-8

15 Clayman L, Rossi E. Fixation of Atrophic Edentulous Mandible Fractures by Bone Plating at the Inferior Border.J Oral Maxillofac Surg. 2011 Jun 13.

16 Pogrel MA . The lower border rib graft for mandibular atrophy. J Oral Maxillofac Surg. 1988 Feb;46(2):95-9.

17 Cranin AN, Sher J, Shpuntoff R. Reconstruction of the edentulous mandible with a lower border graft and subperiosteal implant. J Oral Maxillofac Surg. 1988 Apr;46(4):264-8.

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18 Gutta R, Waite PD. Cranial bone grafting and simultaneous implants: a submental technique to reconstruct the atrophic mandible. Br J Oral Maxillofac Surg. 2008 Sep;46(6):477-9.

19 Lekkas K, Wes BJ. Absolute augmentation of the extremely atrophic mandible. (A modified technique).J Maxillofac Surg. 1981 May;9(2):103-7.

20 Quinn PD, Kent K, MacAfee KA 2nd. Reconstructing the atrophic mandible with inferior border grafting and implants: a preliminary report. Int J Oral Maxillofac Implants. 1992 Spring;7(1):87-93.

21 Reitman MJ, Brekke JH, Bresner M. Augmentation of the deficient mandible by bone grafting to the inferior border. J Oral Surg. 1976 Oct;34(10):916-8.

22 Ridley MT, Mason KG .Resorption of rib graft to inferior border of the mandible. J Oral Surg. 1978 Jul;36(7):546-8

23 Sanders B, Cox R. Inferior-border rib grafting for augmentation of the atrophic edentulous mandible.

J Oral Surg. 1976 Oct;34(10):897-900.24 Sanders B Rib grafting to the inferior border of the mandible. J Oral Surg. 1978

Sep;36(9):669.25 Sanders B, Beumer J 3rd. Augmentation rib grafting to the inferior border of

the atrophic edentulous mandible: a 5-year experience. J Prosthet Dent. 1982 Jan;47(1):16-22

26 Sanders B. Augmentation rib grafting to the inferior border of the mandible. Head Neck Surg. 1982 Mar-Apr;4(4):324-9.

Summary, general discussion, conclusions and future perspectives7

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Summ

ary, conclusions and future perspectives.Chapter 7

7-1. SummaryIn the introduction the aetiology of bone resorption, classification of the resorbed alveolar ridge and the physical, functional and psychological consequences of edentulism are briefly presented. An overview of pre-prosthetic techniques for treatment of the edentulous mandible is given. Moreover, instalment of dental implants in order to preserve edentulous bone and improvement of the retention of the dental prosthesis are mentioned.

In Chapter 1 attention is paid to distraction osteogenesis and its application in cases of severe mandibular atrophy (vertical distraction osteogenesis [VDO]). The differences between the extra osseous (EOD) and the intra osseous distraction (IOD) device are presented. The aims of the study are formulated.

• Which therapy is the clinician’s first choice when restoring the edentulous mandible.(chapter 2)

• In the treatment of patients suffering from extremely resorbed mandibles, does the intra-osseous device (IOD) show better results compared with the extra-osseous device (EOD) as an augmentation method? (chapter 3)

• What complications are associated with VDO conducted with an EOD? (chapter 4)

• What is the vector of distraction using the EOD? (chapter 5)

In Chapter 2 an inventory, conducted in the Netherlands, is presented in order to evaluate which therapy is the clinician’s first choice, when restoring the edentulous mandible. A questionnaire was sent to all Dutch oral- and maxillofacial surgeons. As part of the questionnaire, the surgeons were invited to treat five virtual edentulous patients, differing only in mandibular residual height.

In the case of a sufficient residual height of 15 mm all surgeons were in favour of inserting only two implants, to anchor an overdenture. When the residual height was 12 mm, 10% of the surgeons would choose to carry out an augmentation procedure. If a patient presented with a mandibular height of 10 mm, 40% of the surgeons would already carry out an augmentation procedure. Most of the surgeons (80%) preferred the (anterior) iliac crest as a donor site. The choice of “whether or not to augment” was not influenced by the surgeon’s age; however, it was influenced where they trained. Surgeons, who had trained in Groningen, were more in favour of installing short implants in mandibles with reduced vertical height.

In Chapter 3 it is stated that for implant placement in severe atrophic edentulous mandibles, distraction osteogenesis (VDO) can be used, to gain sufficient bone height. The efficacy of extra-osseous and intra-osseous devices is evaluated. In a retrospective study, 45 patients treated with an extra-osseous device (EOD) are compared with 43 patients treated with an intra-osseous device (IOD).

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From a statistical point of view, both patient groups were comparable with regard to age and sex ratio. The gained bone height was higher for the IOD group (9.8 mm) than for the EOD group (6.0 mm). A significantly higher degree of backward tilting of the device was observed in the EOD group (12.1º), compared with the IOD group (3.0º). There were also significantly more fractures of the basal bone segment and sensory disturbances of the chin area in the EOD group than in the IOD group.

In Chapter 4 complications associated with VDO are described. This study outlines 45 patients suffering from atrophied edentulous mandibles with a vertical height varying between 7.3 and 15.8 mm, who were treated by VDO. The mean follow-up period was 3 years, ranging from 1 to 7 years. Associated complications, as occurred during instalment of the distractor device, during the vertical distraction period and the consolidation phase, as well as after dental implant placement, are evaluated.

The observed complications were: early fractures (2%), late fractures (17%), bleeding or haematoma (4%), infection (6%), skin perforation (2%), mucosal dehiscence (8%), sensory disturbances (28%), sagging chin (13%), and failure of dental implants (13%). In 10 patients, two complications were seen in each patient and in one patient, as many as three complications were seen. All complications occurred in the first year.

In Chapter 5 VDO, as a method of restoring vertical bone height in atrophic mandibles, is studied by means of cephalometric radiographs, that were obtained pre-operatively, immediately after the installation of the distractor device, at the end of the active distraction period (1–2 weeks), before placement of implants, after a consolidation period of 12 weeks and annually thereafter.

Particular attention is paid to the change in position of the upper segment in relation to the basal segment after active distraction. To monitor the position of the distracted upper bone segment, both the improvement in bone height and the angle of the distracted upper bone segment are scored, using the Menton-Pogonion line as a reference plane.

In Chapter 6 a patient is presented with a residual alveolar ridge in the symphyseal area of 8 mm. After performing VDO, 1 day post-operatively, fracturing of the mandible and, consequently, dislocation of the distractor device occurred. The fracture was located on the right side of the mandibular body in the basal segment. Before healing of the fracture was achieved, four surgical interventions were necessary. Removal of the distractor device and rigid fixation were followed by sequestrectomy, additional fixation and acrylic splint fixation due to compromised wound healing. Finally, reconstruction was accomplished by positioning a sub-mental bone graft. Ultimately, after a healing period of 5 months, two endosseous implants were installed.

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It is concluded, that reinforcement of the mandible by augmentation in the sub-mental area seems to be a good method after fracture healing and allows implant instalment in a second stage.

7-2. General discussionIn chapter 2 is mentioned that overdenture supported on two interforaminal implants is reimbursed by the Dutch health insurance. Therefore this treatment modality is very popular in the Netherlands. From a cost perspective and to minimize co-morbidity, surgeons should be more reluctant to carry out augmentation procedures, to restore the resorbed edentulous mandible, as it is reported in the literature, that even in mandibles with a residual height of 10 mm or less, solely placing of implants (thus without a prior augmentation procedure) is a reliable treatment option.

Comparing IOD and EOD in chapter 3, the IOD group scored significantly better on gained bone height, backward tilting of the device, occurrence of fractures, and post-operative sensory disturbances. Despite the fact that the mean pre-operative bone height for the IOD group was substantially higher (18.6 mm) than for the EOD group (11.9 mm), it may be concluded that for augmentation procedures of the edentulous mandible, the IOD is more favourable.

Nevertheless in chapter 4 is settled that VDO to restore the vertical bone height in patients with mandibular atrophy is a surgically delicate technique with a high risk of various complications. The likelihood of the most striking complication, fracture, increases with decreasing residual bone height.

As described in chapter 5, using VDO for restoring an atrophic mandibular ridge, in nearly all the patients was a backwards rotation of the segment with lingual tipping of the upper segment by a mean of 12º, which means, that in such cases only 87% of the maximum gain in bone height could be achieved. As a consequence of the backward tipping of the top of the distracted alveolar ridge, the position of the implants was also more lingually directed. However, in all cases, sufficient bone volume was achieved, to allow implant placement.

Distraction osteogenesis can be a successful method for restoring atrophic mandibles, in order to gain sufficient bone volume, to allow implant placement. However, the vector of distraction is an unpredictable factor.

7-3. Conclusions in relation to the aims of the studyThe question, as to which therapy is the clinician’s first choice, when restoring the edentulous mandible in cases of severe atrophy, cannot be answered clearly; no favourable treatment among Dutch oral- and maxillofacial surgeons could be elucidated. It seems to depend on former training and

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experience. Health insurance regulations also have an important influence on the choice of treatment. There is no evidence-based treatment strategy, whether to augment or to solely place short dental implants, although there is a trend in favour of the latter treatment approach.

When VDO is used as a treatment method for gaining bone volume in the case of extremely resorbed mandibles, the IOD has better results compared to the EOD. The better performance of the IOD is based on gained bone height, less tilting of the device, less extensive surgery causing less additional complications.

To date, complications associated with VDO carried out with an EOD are fracture, sensory disturbances and backward tilting of the device. The vector of distraction using the EOD is mostly lingually orientated. Despite the unpredictable amount of tipping of the upper segment during distraction, after treatment, sufficient bone is available for implant placement.

7-3. Future social perspectivesIssues such as; bone resorption, concomitant retention, drawback of dentures, associated difficulties of pain, diminished chewing function and changed facial appearance, are still valid today. For many patients, loss of teeth is the beginning of a period of dental disability. Dealing with this problem is currently more related to the possibility of the patient accepting the inconvenience of the limitations, than the opportunity of the dental professionals to solve the problem. Improvement of function and reconstruction of the lost tissues remains a challenge for dentists and maxillofacial surgeons.

While it is true, that the percentage of edentulous adults has declined over the past 30 years, one must take demographic trends into account, such as the increase in number and age of the older population. In contrast to popular belief, the need and demand for complete dentures will increase until 2020, as the baby boom generation matures into the upper age groups. Middle-aged (45–64 years) population groups have experienced improved oral health compared with previous generations and the percentage of edentulous adults can be expected to further decline. 1 However, there will be a large increase in the number of older adults. Literature corroborates, that the 10% decline in edentulism, experienced each decade for the past 30 years, will be more than counterbalanced by the 79 % increase in the adult population older than 55 years.

Poor satisfaction with dentures is associated with poor denture stability. As the extent of residual ridge resorption in the mandible is one of the most important factors, that has increased dissatisfaction with lower complete dentures, it is important to inhibit the progression of resorption by preventing tooth loss or by using implant-retained dentures. 2 Besides,

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it has been proven, that there is a significant improvement in satisfaction and health-related quality of life in patients, who receive implant-retained dentures. Therefore, it is of extreme importance to monitor the edentulous patient and to inform them of the risks of “waiting too long”. Ultimately, the patient can postpone implant placement to such an extent, that an augmentation procedure can no longer be avoided. Timely replacement of worn out or inadequate dentures can be realized by regular recall of all denture wearers to the dental practice. The assumption of some patients, that they will “never visit a dentist anymore” after losing their teeth, must be avoided.

In the future, special attention must be paid to the increasing population of dependent elderly people with pre-implant surgery and/or dental implants. These patients need specific oral health care by dental hygienists, care providers and volunteer helpers. Difficult anchorage structures must be changed to easier cleaning constructions, such as locator abutments. If necessary, the supra structures can be removed and putting the implants to sleep

8-4. Future surgical perspectivesAlthough advanced implant technology with better performance of short implants might provide opportunities for patients with atrophic mandibles, reconstruction of the lost (bony) tissues to physiological proportions is still an attractive goal for restoring function and aesthetics. As such, there is a prominent place for mandibular bone augmentation techniques. Augmentation with (autologous) bone, as onlay, as well as the lower border procedure, gives the possibility of mandibular reinforcement, besides the possibility of implant placement.

Indications for augmentation techniques are aesthetic reasons such as reduced facial height, functional reasons, such as bulky lingual soft tissues and a negative bony ridge, as well as insufficient or missing attached gingiva. A high knife-edge ridge, unfit for implant placement, can be enhanced by augmentation. Depending on the advantages and disadvantages of the different techniques, sandwich osteotomy, onlay or the lower border method and VDO are still valuable practices for improving the denture-bearing area.

One of the main reasons for practicing VDO is the avoidance of a bone graft and the possible related donor-site morbidity. The goal of VDO is to regenerate bone tissue by slowly lifting the upper segment from the basal segment. VDO offers the possibility of a pedicled flap, allowing for periosteal blood supply. Formation of new bone in the distraction gap is related to ingrowth and the presence of blood vessels. 5 Therefore, post-operative resorption of the gained bone should be considerably less than it would be with a free bone graft.

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However, a minimum of bone height should be present, to allow splitting of the bone in a upper and basal segment.

In the future, bone tissue engineering might offer an alternative strategy for restoring damaged, diseased and resorbed bone tissue. With the three-dimensional (3D) computed tomography scan a defect can be converted to a CAD file, in order to make a 3D-printed scaffold according to the defect. A number of biodegradable and bioresorbable materials, as well as scaffold designs, have been experimentally and/or clinically studied. These scaffolds may host osteogenic stem cells. With these, embedded cell tissue cultures can grow in vitro and probably, through ingrowth of blood vessels, support tissue formation in vivo. This frame of expected developments is clear; however, translation of the laboratory model into a clinically appropriate situation will take many years of investigation.

In the meantime, pre-implant surgery will proceed, based on the many years of experience with pre-prosthetic surgery and implant-related techniques. 6 The lower border augmentation technique must be mentioned, not only as a method of trouble shooting after fracture, but also as a valuable mean, to create more bone volume allowing for implant placement. In addition, the provision of short implant-supported prostheses in patients with atrophic alveolar ridges appears to be a successful treatment option in the short term; however, more scientific evidence is needed for the long term.

Based on Ilizarovs principles, McCarthy introduced clinically the application of craniofacial distraction osteogenesis in 1994. 7 Enthusiastically, many clinicians tried this concept in their surgical field. However, also the distraction technique followed the principles of a hype circle (Fig.1.); a

Figure 1: Hype circle. (Gartner, Inc)

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graphic representation of the maturity, adoption and social application of specific technologies. This term was introduced by Gartner, Inc. (Stamford, Connecticut, United States ) to characterize the over-enthusiasm or “hype” and subsequent disappointment, that typically happens with the introduction of new technologies. After an initial peak of inflated expectations, the limits of the mandibular distraction technique, as denoted in this thesis, became clear (trough of disillusionment). The future will elucidate, if vertical distraction of the atrophic jaw, with respect to the limitations as described in this thesis, will continue to exist.

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Reference

1 Douglass CW,Shih A, Ostry L: Will there be a need for complete dentures in the United States in 2020? J of Prosthe Dent 2002;875-8.

2 Huumonen S,Haikola B,Oikarinen K, Söderholm AL,Remes-Lyly T,Sipilä K. Residual ridge resorption, lower denture stabilty and complaints among edentulous individuals. J Oral Rehabil. 2012 May; 39(5):384-390.

3 Warpeha WS Jr. Expanding prosthodontic services to the older patient in dental practices. Northwest Dent. 2011 Nov-Dec;90 (6):21-4.

4 Visser A, de Baat C, Hoeksema AR, Vissink A. Oral implants in dependent elderly persons: blessing or burden? Gerodontology 2011 Mar, 28(1):76-80.

5 Amir LR, Becking AG, Jovanovic A, Perdijk FBT, Everts V, Bronckers ALJJ. Formation of new bone during vertical distraction osteogenesis of the human mandible is related to the presence of blood vessels Clin. Oral. Impl. Res. 17, 2006; 410-416

6 Cawood JI, Stoelinga PJW, Blackburn TK. Int. J. Oral Maxillofac. Surg. 2007; 36: 377-385.

7 Mc Carthy JG: The role of distraction osteogenesis in the reconstruction of the mandible in unilateral craniofacial microsomia, Clin Plas Surg 21: 625, 1994.

Samenvatting, conclusies en toekomstperspectief.8

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Samenvatting, conclusies en toekom

stperspectief.Chapter 8

8-1. SamenvattingIn de introductie wordt de etiologie van botresorptie beschreven. Tevens worden de fysieke, functionele en ook psychologische gevolgen van tandeloosheid behandeld, alsmede een classificatie voor geresorbeerd alveolair bot. Eén van de gevolgen van tandeloosheid is, dat de onderkaak gaat “slijten”. Door de belasting van het kunstgebit neemt met name de bothoogte af, zodat het dragen van een kunstgebit leidt tot vele klachten, zoals het loskomen van het gebit maar ook pijn.

Er zijn de afgelopen jaren talloze chirurgische, zogenaamde pré-prothetische, technieken geïntroduceerd, met als doel om in tweede instantie een beter functionerend kunstgebit te kunnen vervaardigen. Een overzicht van deze technieken wordt in deze inleiding gepresenteerd. Tevens wordt de rol van tandwortelimplantaten besproken, een middel om de tandeloze onderkaak voor verdere resorptie te behoeden, als ook om de retentie van de gebitsprothese in de onderkaak te verbeteren.

In hoofdstuk 1 wordt aandacht besteed aan distractie osteogenese en de toepassing hiervan bij patiënten met een ernstige onderkaakslijtage (atrofie). Het verschil tussen de extra-osseous (EOD) en de intra-osseous (IOD) distractor wordt besproken. Tot slot worden de onderzoeksvragen, die de basis voor deze thesis vormen, geformuleerd.

• Welke therapiekeuze maakt de clinicus bij de behandeling van de ernstig geatrofieerde onderkaak? (hoofdstuk 2)

• Wanneer we patiënten met een ernstig geatrofieerde onderkaak behandelen met behulp van distractie osteogenese bestaat de keus om gebruik te maken van een EOD dan wel een IOD. Welke distractor laat de beste resultaten zien? (hoofdstuk 3)

• Welke complicaties kunnen voorkomen bij het gebruik van een EOD? (hoofdstuk 4)

• Wat is de vector van distractie bij het gebruik van de EOD? (hoofdstuk 5)

In hoofdstuk 2 wordt een enquête gepresenteerd, die werd afgenomen onder alle Nederlandse Mond, Kaak- en Aangezicht- (MKA)chirurgen. Zij werden uitgenodigd om vijf virtuele tandeloze patiënten te behandelen met verschillende onderkaakhoogten. Het doel was om de therapiekeuze voor het herstellen van de tandeloze onderkaak te evalueren.

Bij een ruime kaakhoogte (15mm) kozen alle MKA-chirurgen om uitsluitend twee implantaten te plaatsen als basis voor een kunstgebit. Bij een kaakhoogte van 12 mm gaf 10% van de MKA-chirurgen aan eerst te kiezen voor een verhoging van de onderkaak, om in tweede instantie implantaten te kunnen plaatsen. Bij een kaakhoogte van 10 mm werd al door 40% van de MKA-chirurgen eerst een kaakverhoging operatie uitgevoerd, alvorens implantaten te plaatsen.

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De meeste MKA-chirurgen (80%) benoemden de bekkenkam als voorkeursplaats om het bot te oogsten. De keuze om vóór het plaatsen van implantaten “wel of niet” een kaakverhoging operatie uit te voeren werd niet bepaald door de leeftijd van de MKA-chirurg. Wel was de opleidingsplaats van de betreffende MKA-chirurg van invloed op zijn uiteindelijke behandelkeuze. Zo gaven MKA-chirurgen opgeleid in Groningen bij lagere kaakhoogtes vaker de voorkeur aan het plaatsen van korte implantaten.

De overkappingsprothese op twee implantaten, gepositioneerd ter plaatse van de voormalige hoektanden, is in Nederland een populaire behandeling, ook omdat deze wordt vergoed door de ziektekosten-verzekeringen. Opvallend is, dat 40% van de MKA-chirurgen bij een kaakhoogte van 10 mm de voorkeur gaf aan voorafgaande kaakverhoging, terwijl de literatuur aangeeft dat ook de optie van “alleen implantaten plaatsen” ook een betrouwbare behandelmogelijkheid is.

Uit kostenoogpunt en ter voorkoming van een tweede ingreep, nl het oogsten van het bottransplantaat, zouden MKA-chirurgen terughoudender moeten zijn met het verhogen van de matig geslonken tandeloze onderkaak.

In hoofdstuk 3 wordt de Verticale Distractie Osteogenese (VDO) als methode behandeld om, in geval van een ernstig geatrofieerde tandeloze onderkaak, meer botvolume te creëren. De werking van zowel de “extra-osseous” distractor (EOD) als de “intra-osseous” distractor (IOD) werd geëvalueerd.

In een retrospectief onderzoek werden 43 patiënten, behandeld met een IOD, vergeleken met 45 patiënten, die uitgerust werden met een EOD. Beide patiëntengroepen waren, vanuit statistisch oogpunt bekeken, vergelijkbaar qua leeftijd en geslacht. De IOD groep bereikte meer winst in hoogte (9,8 mm) dan de EOD groep (6,0 mm). Het naar achteren kantelen van de distractor bij de IOD groep was minder (3.0º) dan bij de EOD groep (12.1º). Ook werden in vergelijking met de EOD groep bij de IOD groep minder breuken van het basale botsegment gezien en traden in het kingebied minder vaak gevoelsstoornissen op.

Uit bovenstaande blijkt, dat de IOD groep beduidend beter scoorde op punten als ‘bereikte bothoogte’, ‘kanteling van het distractieapparaat’, het ‘optreden van breuken’ en ‘postoperatieve gevoelsstoornissen’. Ondanks het feit, dat de gemiddelde preoperatieve bothoogte voor de IOD groep hoger was (18.6 mm) dan voor de EOD groep (11.9 mm is), kon toch geconcludeerd worden, dat een IOD, in het geval van het verhogen van de tandeloze onderkaak, betere resultaten gaf.

In hoofdstuk 4 worden de aan de EOD gerelateerde complicaties in kaart gebracht. Deze studie vervolgde 45 tandeloze patiënten met een onderkaakhoogte tussen de 7,3 en 15,8 mm. Bij allen vond verticale distractie plaats door middel van een EOD. De follow-up periode varieerde tussen de 1 en 7 jaar met een gemiddelde van 3 jaar. Complicaties bij het

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plaatsen van de distractor, tijdens de periode van verticale distractie en in de consolidatiefase en na implantaat plaatsing, werden geëvalueerd.

De waargenomen complicaties bestonden uit: vroege fracturen (2%), late fracturen (17%), nabloedingen en/of haematoomvorming (4%), infecties (6%), huidperforatie (2%), mucosa dehiscentie (8%), sensibiliteitstoornissen (28%) en het postoperatief ontstaan van een “hangkin”, veroorzaakt door het losmaken van de kinspieren (13%). Ook was sprake van implantaatverlies (13%). Tien patiënten ondervonden twee van bovengenoemde complicaties en één patiënt zelfs drie. Alle complicaties traden op in het eerste jaar.

Concluderend kan gesteld worden, dat distractie met een EOD bij patiënten met een sterk geatrofieerde onderkaak een delicate chirurgische techniek is met een hoog risico op meerdere complicaties. Hoe lager de kaak, hoe meer kans op ontstaan van ernstige complicaties, zoals kaakbreuk.

In hoofdstuk 5 wordt de mate van onderkaakverhoging, zoals bereikt met behulp van een EOD, röntgenologisch beschreven. Schedelprofiel foto’s, die werden gemaakt preoperatief, onmiddellijk na het aanbrengen van de distractor, aan het einde van de periode van actieve distractie (1-2 weken), na een periode van consolidatie van 12 weken, net vóór plaatsing van de implantaten en jaarlijks daarna, werden met elkaar vergeleken.

De gewijzigde positie van het bovenste botsegment ten opzichte van het basale segment, vόόr en ná actieve distractie, kreeg bijzondere aandacht. Met behulp van de lijn Menton-Pogonion als referentielijn werd de positie van het bovenste botsegment, als ook de hoek, die dit segment maakt, gemeten.

Bij bijna alle patiënten werd een achterwaartse rotatie van het bovenste segment gezien, met een gemiddelde van 12 graden. Vervolgens werd berekend, dat hierdoor slechts 87% van de maximale bothoogte werd bereikt. Als gevolg van het achterwaartse kantelen van het bovenste botsegment werd ook de positie van de te plaatsen implantaten meer naar linguaal gedwongen. Bij alle patiënten werd toch voldoende botvolume verkregen om uiteindelijk implantaatplaatsing mogelijk te maken.

Gebruik van een EOD kan succesvol zijn bij de behandeling van atrofische onderkaken. Echter, de vector van distractie blijft een onvoorspelbare factor. In hoofdstuk 6 wordt een patiënt gepresenteerd met een dunne atrofische edentate onderkaak; ter plaatse van de oorspronkelijke hoektanden was nog een resterende bothoogte van slechts 8 mm aanwezig. Eén dag na het aanbrengen van de IOD bleek, dat de onderkaak was gebroken en de distractor verplaatst. De breuk bevond zich aan de rechterkant van de onderkaak in het basale botsegment. Om tot een bevredigend eindresultaat te komen waren uiteindelijke 4 chirurgische ingrepen nodig; verwijdering

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van de distractor en fixatie van de breuk met behulp van osteosynthese materiaal , fixatie van een tweede fractuur, ditmaal aan de linkerzijde, verwijdering van het reeds aangebrachte fixatiemateriaal en het inbinden van een kunststof spalk om de fracturen te immobiliseren en aanbrengen van een autoloog bottransplantaat aan de onderzijde van de onderkaak ter reconstructie. Na een herstelperiode van 5 maanden konden uiteindelijk een tweetal implantaten worden geplaatst.

Geconcludeerd werd, dat, in geval van kaakbreuk, het versterken van de onderkaak door middel van het aanbrengen van een autoloog bottransplantaat aan de onderzijde een goede methode blijkt te zijn; niet alleen om de kaakcontinuïteit te herstellen, maar ook om in tweede instantie implantaatplaatsing mogelijk te maken.

8-2. Conclusies De vraag, welke therapie de MKA-chirurg kiest bij de behandeling van de tandeloze patiënt met ernstige onderkaak atrofie, kan niet eenduidig worden beantwoord. Opleiding en ervaring van de MKA-chirurg lijken een rol te spelen. Wat betreft de behandelkeuze ten aanzien van de edentate onderkaak bestaat geen “evidence based” beleid, bij welke kaakhoogte kan worden volstaan met het plaatsen van alleen korte implantaten en bij welke kaakhoogte eerst opgehoogd moet worden. Er is wel een trend ten gunste van het plaatsen van korte implantaten.

Als behandelmethode voor verhoging van de geresorbeerde onderkaak laat de intra-osseous distractor (IOD) betere resultaten zien dan de extra-osseous distractor (EOD). De betere prestaties van het IOD zijn gebaseerd op bereikte bothoogte, minder achterwaartse kanteling van de distractor, minder uitgebreide chirurgie en het minder optreden van complicaties.

De complicaties van verticale distractie uitgevoerd met een EOD kunnen bestaan uit kaakbreuk en sensibiliteitstoornissen.

De vector van distractie met de EOD is meestal linguaal georiënteerd. Onvoorspelbaar blijft de mate van kanteling. Uiteindelijk is na distractie altijd wel voldoende bot beschikbaar voor het plaatsen van twee implantaten.

8-3. Toekomst perspectief tandeloze patiëntDe problemen van de tandeloze patiënt met sterke slijtage van de onderkaak, zoals het loszitten van het ondergebit en de daarbij behorende pijn, afgenomen kauwfunctie en gewijzigde gezichtsfysionomie, zijn ook vandaag de dag nog steeds actueel. Voor veel patiënten is het verlies van tanden het begin van een periode van tandheelkundige invaliditeit. Dat uiteindelijk toch veel patiënten tevreden zijn met hun kunstgebit ligt meer aan het aanpassingsvermogen van de patiënt, dan aan de mogelijkheid van

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tandheelkundige professionals om de gebitsproblemen op te lossen.

Hoewel het aantal tandeloze volwassenen de afgelopen 30 jaar is afgenomen, dient men ook de demografische veranderingen in het oog houden, zoals de toename van het aantal ouderen. Uit de literatuur blijkt namelijk, dat, in tegenstelling tot wat wel wordt gedacht, de vraag naar volledige gebitsprotheses tot 2020 zal toenemen; de afname van het aantal tandelozen zal worden tenietgedaan door de toename van de bevolking ouder dan 55 jaar.1

Ontevredenheid over het kunstgebit hangt samen met de pasvorm en de stabiliteit. Een mogelijkheid om het aanwezige kaakbot in stand te houden is op tijd tandwortelimplantaten plaatsen ten dienste van een implantaat- afgesteund kunstgebit. 2 Hiermee ervaart de patiënt een aanzienlijke verbetering in kwaliteit van leven. Daarom is het aanbevelenswaardig om de tandeloze patiënt te blijven controleren; hem uitgebreid te informeren over de risico’s van “te lang wachten”. 3 Het idee van sommige patiënten “dat ze voor altijd van de tandarts af zijn” na het verliezen van hun tanden, moet worden bestreden.

In de toekomst dient speciale aandacht te worden besteed aan de toenemende groep afhankelijke ouderen, die pré-implantologische chirurgie hebben ondergaan en/of waarbij tandwortelimplantaten zijn geplaatst. Deze patiëntengroep blijft gespecialiseerde mondzorg nodig hebben. Ingewikkelde suprastructuren moeten worden vermeden en zo nodig vervangen worden door eenvoudig te reinigen constructies, zoals drukknoppen. Desnoods kan de suprastructuur verwijderd worden en de implantaten “slapend” gemaakt worden. 4

8-4. Toekomstperspectief tandeloze patiënt vanuit chirurgisch oogpuntHoewel het plaatsen van korte implantaten steeds populairder wordt, blijven er nog vragen onbeantwoord. Zo is nog onbekend of, indien er peri-implantitis rondom deze korte implantaten optreedt, dit gepaard zal gaan met een verhoogde kans op kaakbreuk. Daarom is vervanging van het verloren (bot)weefsel nog steeds een aantrekkelijke behandeloptie voor de extreem geresorbeerde onderkaak. Het bottransplantaat kan als onlay, d.w.z. bovenop de kaak aangebracht worden, als ook aan de onderzijde van de kaak (lower border techniek).

Indicaties voor het verhogen van de kaak kunnen ook esthetisch van aard zijn, zoals een ingevallen gezicht of vanwege functionele redenen: een uitpuilende mondbodem en negatieve kaakbotrand of de afwezigheid van aangehechte gingiva. Zo kan een hoge messcherpe kaakbotrand, ongeschikt voor de plaatsing van implantaten, worden verbreed door het aanbrengen van botblokken.

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Eén van de belangrijkste redenen om VDO toe te passen was het vermijden van het oogsten van een bottransplantaat en de daarbij optredende ongemakken, zoals mobiliteitsklachten, pijn en verlengde ziekenhuisopname. Het doel van VDO is het regenereren van botweefsel door het patiënteigen bot. Hierbij wordt de botgroei gestimuleerd door ingroei van bloedvaten in de distractiespleet. 5 Het nieuwe bot bevindt zich tussen de twee oude botlagen, waardoor de postoperatieve resorptie van het verkregen bot aanzienlijk minder is, dan bij een vrij bottransplantaat. Echter, om de kaak horizontaal te kunnen splitsen, zal een minimum bothoogte nodig zijn.

Zou in de toekomst bot ‘tissue engineering’ uitkomst kunnen bieden? CT-scan’s van botdefecten kunnen worden geconverteerd naar CAD-bestanden om vervolgens een biologisch afbreekbaar poreuze matrijs te printen, die geladen kan worden met patiënteigen gekweekte botcellen. Hoewel op het niveau van dierexperimenten successen zijn geboekt, laat een echte doorbraak naar de kliniek nog op zich wachten.

Tot die tijd zal pré-implantologische chirurgie, gebaseerd op vele jaren ervaring uit de pré-prothetische chirurgie, nog steeds toegepast worden. 6 Hierbij zal elke specifieke techniek zijn eigen toepassingsgebied hebben. Ook VDO kan een belangrijke rol spelen. Het plaatsen van een autoloog bottransplantaat aan de onderzijde van de kaak kan een oplossing zijn, in het geval van een fractuur van de onderkaak, maar ook om meer bot te creëren voor het plaatsen van implantaten. Het plaatsen van een implantaat gedragen prothese op zeer korte implantaten lijkt sinds kort een succesvolle methode te zijn, maar moet op de langere termijn nog haar betrouwbaarheid bewijzen.

Figure 1: Hype circle. (Gartner, Inc)

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Op basis van de grondbeginselen opgesteld door Ilizarov, beschreef McCarthy in 1994 de toepassing van distractie osteogenese bij craniofaciale afwijkingen. 7 Enthousiast geworden door de successen pasten vele clinici deze technieken toe. Echter, distractie osteogenese volgt de principes van de “hype” circle. Dit is een grafische weergave van het ontstaan, het ontwikkelingstraject en de uiteindelijke toepassing van nieuwe technologieën. De term “hype circle” werd geïntroduceerd door Gartner, Inc. (Stamford, Connecticut, United States) en karakteriseert de “hype” of wel het extreem enthousiast zijn over een nieuwe technologie, gevolgd door een traject van teleurstellingen. Deze teleurstellingen gelden juist voor de introductie van nieuwe technologieën. Na een aanvankelijk hoogtepunt van opgeblazen verwachtingen zijn de beperkingen van VDO, zoals beschreven in deze thesis, duidelijk. (Trough of Disillusionment) De tijd zal leren of VDO binnen de beschreven grenzen zal blijven bestaan.

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Referenties

1 Douglass CW,Shih A, Ostry L: Will there be a need for complete dentures in the United States in 2020? J of Prosthe Dent 2002;875-8.

2 Huumonen S,Haikola B,Oikarinen K, Söderholm AL,Remes-Lyly T,Sipilä K. Residual ridge resorption, lower denture stabilty and complaints among edentulous individuals. J Oral Rehabil. 2012 May; 39(5):384-390.

3 Warpeha WS Jr. Expanding prosthodontic services to the older patient in dental practices. Northwest Dent. 2011 Nov-Dec;90 (6):21-4.

4 Visser A, de Baat C, Hoeksema AR, Vissink A. Oral implants in dependent elderly persons: blessing or burden? Gerodontology 2011 Mar, 28(1):76-80.

5 Amir LR, Becking AG, Jovanovic A, Perdijk FBT, Everts V, Bronckers ALJJ. Formation of new bone during vertical distraction osteogenesis of the human mandible is related to the presence of blood vessels Clin. Oral. Impl. Res. 17, 2006; 410-416

6 Cawood JI, Stoelinga PJW, Blackburn TK. Int. J. Oral Maxillofac. Surg. 2007; 36: 377-385.

7 Mc Carthy JG: The role of distraction osteogenesis in the reconstruction of the mandible in unilateral craniofacial microsomia, Clin Plas Surg 21: 625, 1994.

List of publications.

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List of publications:

P.J. van Strijen, F.B.T. Perdijk. Mandibular advancement by means of Intra-oral DistractionJournal of Cranio-Maxillofacial Surgery (Suppl. No. 1) 1997; vol. 26-75

P.J. van Strijen, F.B.T. Perdijk, H. Breuning. Distractie osteogenese. Een nieuwe ontwikkeling in de aangezichtschirurgieNed Tijdschr Tandheelkd 1998; 105; 129-131

P.J. van Strijen, F.B.T. Perdijk. Bi-lateral sagittal monocortical distraction for mandibular retrognathism.International Proceedings; cranial and facial bone distraction processes 1997; 121-126

P.J. van Strijen, F.B.T. Perdijk, H. Breuning. Mandibular stability one year after bilateral distraction of the mandibleJournal of Cranio-Maxillofacial Surgery (Suppl.) 1998. Vol: 26 -198

P.J. van Strijen, F.B.T. Perdijk, H. Breuning. Osteo-distraction in class II deficiencies; The treatment of choice?International Proceedings; cranial and facial bone distraction processes 1999; 249-259 ISBN 88-323-0617-4

H. Breuning, P.J. van Strijen, F.B.T. Perdijk. Orthodontic treatment planning for distractionInternational Proceedings; cranial and facial bone distraction processes 1999; 259-263 ISBN 88-323-0617-4

F.B.T. Perdijk , P.J. van Strijen. Correction of severe mandibular atrophy by means of distraction osteogenesis.International Proceedings; cranial and facial bone distraction processes 1999; 157-161 ISBN 88-323-0617-4

P.J. van Strijen, F.B.T. Perdijk. Distractie osteogenese en de tandheelkunde. Het Tandheelkundig Jaar 1999;115-126 ISBN 90 313 3017 5

P.J. van Strijen, F.B.T. Perdijk, E. Becking, H. Breuning. Distraction osteogenesis for mandibular advancement.Int. J. Oral Maxillofac. Surg. 2000; 29: 81-85

P.J. van Strijen, F.B.T. Perdijk, K. H. Breuning. Relapse following distraction osteogenesis in patients with class II mandibular hypoplasia.Journal of Cranio-Maxillofacial Surgery (Suppl. 3) 2000; 28: 114-115

F.B.T. Perdijk , P.J. van Strijen. Augmentation of Severe Mandibular Atrophy by Vertical Distraction OsteogenesisCraniofacial distraction Osteogenesis. Samchukov M.L., Cope J.B., Cherkashin A.M., editors. Mosby,Inc. 2001;433-437 ISBN 0-323-01134-

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F.B.T. Perdijk , P.J. van Strijen. Results of Vertikal Alveolar Distraction.International Proceedings: cranial and facial bone distraction processes 2001; 89-93. Monduzzi Editore.

P.J. van Strijen, K. H. Breuning, F.B.T. Perdijk, D.B. Tuinzing. Advantages and Disadvantages of conventional Versus Distraction Treatment for Class II CorrectionInternational Proceedings: cranial and facial bone distraction processes 2001; 585-590. Monduzzi Editore.

F.B.T. Perdijk. Verticale distractie als voorbereiding voor implantologie in de atrofische onderkaakBulletin NVOI, 7e jaargang no 3, oktober 20

K.H. Breuning, J. de Lange, F.B.T. Perdijk. Een fout in de afdrukprocedure? Ned. Tijdschrift voor Tandheelkunde, 2003; 110: 159-160

P.J. Van Strijen, K.H. Breuning, A.G. Becking, F.B.T. Perdijk , D.B. Tuinzing. Cost, operation and hospitalisation times in distraction osteogenesis versus sagittal split osteotomyJournal of Cranio-Maxillofacial Surgery (2003) 31, 42-45

van Strijen PJ, Breuning KH, Becking AG, Perdijk FB, Tuinzing DB. Complications in bilateral mandibular distraction osteogenesis using internal devices.Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2003 Oct;96(4):392-7

Amir LR, Becking AG, Jovanovic A, Perdijk FBT, Everts V, Bronckers ALJJ. Vertical distraction osteogenesis in the human mandible: a prospective morphometric studyClin. Oral. Impl. Res. 17, 2006; 417-425

Amir LR, Becking AG, Jovanovic A, Perdijk FBT, Everts V, Bronckers ALJJ. Formation of new bone during vertical distraction osteogenesis of the human mandible is related to the presence of blood vesselsClin. Oral. Impl. Res. 17, 2006; 410-416

KH Breuning, PJ van Strijen, FBT Perdijk, MO de Lange. The Power of Orthodontics and Maxillary Surgery5 th International Congress of Maxillofacial and Craniofacial Distraction. Medimond International Proceedings 2006;127-132

PJ van Strijen, KH Breuning, FBT Perdijk, MO de Lange. Intra-oral Maxillary Distraction5 th International Congress of Maxillofacial and Craniofacial Distraction. Medimond International Proceedings 2006;139-146.

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List of publications:

L R Amir , A Jovanovic , FBT Perdijk , S Toyosawa , V Everts , ALJJ Bronckers. Immunolocalization of SIBLING and RUNX2 Proteins During Vertical Distraction Osteogenesis in the Human Mandible.J Histochem Cytochem. 2007 Jul 11; : 17625229

Perdijk FB, Meijer GJ, Strijen PJ, Koole R. Complications in alveolar distraction osteogenesis of the atrophic mandible.Int J Oral Maxillofac Surg. 2007 Oct;36(10):916-21.

P J. van Strijen, O. Hamburg, , K. H Breuning, F. B.T. Perdijk, M. O. de Lange, S. Bolouri. Psychological effects on children undergoing mandibular elongation by distraction osteogenesis. Int. J. Oral Maxillofac. Surg. 2007 (vol 36), 11: 1002

Breuning KH, de Lange M, van Strijen PJ, Perdijk FB, Bolouri S. Orthodontie en verticale distractie osteogenese van de maxilla.Ned Tijdschr Tandheelkd. 2008 Oct;115(10):553-6.

F.B.T. Perdijk, G.J. Meijer. Verhoging van de geresorbeerde onderkaak met behulp van distractie osteogenese.Praktijkboek Tandheelkunde. Afl. 12/ oktober 2008.

Perdijk FB, Meijer GJ, van Strijen PJ, Koole R. Effect of extraosseous devices designed for vertical distraction of extreme resorbed mandibles on backward rotation of upper bone segmnts.British Journal of Oral & Maxillofacial Surgery 47 (2009), pp. 31-36

Frits B.T. Perdijk, Gert J. Meijer, Ewald M. Bronkhorst & Ron Koole. Implants in the severely resorbed mandibles: whether or not to augment? What is the clinician’s preference? Oral and Maxillofacial Surgery: Volume 15, Issue 4 (2011), Page 225-231

F.B.T. Perdijk, G.J. Meijer, Ch. Krenkel, R. Koole. The use of intra-osseous versus extra-osseous distraction devices in atrophic mandibles.Int J Oral Maxillofac Surg. 2012; 41:521-526.

Dankwoord

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Frits & Peter

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Dankw

oord

Eind jaren negentig maakten Peter van Strijen en ik kennis met de distractie osteogenese. Deze oude techniek, welke in Amerika, door het gebruik van kleine distractoren, opnieuw was geïntroduceerd, leek veelbelovend. Wij waren ook enthousiast en behandelden patiënten met deze nieuwe methode, bezochten de eerste Europese distractie congressen, hielden lezingen en ontwierpen zelf een aantal distractoren, die door een firma op de markt werd gebracht. Er ontwikkelden zich twee richtingen: de horizontale distractie van de onderkaak bij de klasse II afwijkingen ( proefschrift Peter, 2003) en de verticale distractie als pré-implantologische ingreep voor de behandeling van de geatrofieerde processus alveolaris.

Zittend aan de rand van een tropisch zwembad na een succesvolle voordracht over de verticale distractie, ontstond het idee om over dit onderwerp een proefschrift te schrijven. Later tijdens de vele uren, die nodig waren om dit proefschrift te schrijven, heb ik nog menigmaal teruggedacht aan dát tropische zwembad.

Dank aan alle patiënten, die behandeld zijn met VDO. De verschillende behandelopties zijn altijd besproken. Het vertrouwen in deze methode maakte, dat U koos voor deze aanpak. Jarenlange nacontrole bevestigde een toename van “quality of life”. Bij diegene, waarbij een complicatie optrad, werd uiteindelijk altijd gezamenlijk een goed resultaat bereikt.

Hooggeleerde Meijer, beste Gert, het was geen toeval, dat ook jij aan de rand van bovengenoemd tropisch zwembad zat! Zonder jouw begeleiding en steun was het niets geworden. Als “groentje” in de wetenschap leerde je mij kritisch te kijken en na iedere revisie van een artikel ging de kwaliteit met sprongen vooruit. Ik denk met veel genoegen terug aan de vele maandagavonden bij “Valdin” , waar naast een voedzame maaltijd, voortgang, verbeteringen en verder beleid werden uitgedacht. Startte ik zo’n avond meestal met zorgen over haalbaarheid en dergelijke, jouw enthousiasme en gedrevenheid maakte, dat ik aan het eind van de avond vol adrenaline naar huis reed om opgeladen verder te gaan met dit project. Heel erg veel dank!

Hooggeleerde Koole, beste Ron, veel dank voor jouw vertrouwen in dit onderzoek. Helder filosoferend over de toepassing van VDO techniek zijn we naar een eindconclusie gekomen. Perifeer werkend heb ik altijd een speciale band met MKA-Utrecht gehad. Het is een grote eer om bij jou in Utrecht te mogen promoveren.

Zeergeleerde van Strijen, beste Peter, ” brother in distraction”, samen hebben we jaren aan distractie gewerkt, patiënten geopereerd, operaties uitgedacht, distractoren ontwikkeld en lezingen gehouden. Never a dull moment! Deze extra impuls maakt, dat ook de dagelijkse praktijk interessant blijft.

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Zeergeleerde Amir, dear Lisa, your work and results at the Department of Oral Cell Biology, ACTA, Amsterdam, concerning the biological responses of tissue to mechanical stimulation (ea. distraction), added an interesting aspect to the clinical application of distraction. It was a pleasure to supply the bone biopsies and work together.

Zeergeleerde Jovanovic, beste Andreas, samen leverden wij de botbiopten van onze distractie patiënten voor het onderzoek van Lisa Amir. De gezamenlijke interesse in deze materie was inspirerend om door te gaan.

Professor Krenkel, dear Christian, working in the same field of interest, it was a great pleasure to share knowledge. I will never forget your hospitality at your department in Salzburg, the personal training in “endodistraction” and the possibility to compare scientific data.

Hooggeleerde Hakman, beste Eelco, door jou kon de speciale band tussen Salzburg en Ede worden verstevigd. Dank voor jouw inbreng. Een gezamenlijk artikel was bijna rijp om meegenomen te worden in dit proefschrift. De insteek van dat artikel blijft een boeiend onderwerp.

Zeergeleerde Bronkhorst, beste Ewald, data aanleveren is één aspect; verrassend is dat de verwachte uitkomsten, na statistische bewerking van de gegevens, soms moeten worden bijgesteld. Dank voor jouw vaak snelle bijdrage op dit gebied.

Zeergeleerde Meijndert, geleerde Wijmenga, beste Leo en Jan-Peter, ook jullie waren enthousiast over de mogelijkheden van VDO en het gebruik van de ontwikkelde distractor. De grenzen van de mogelijkheden hebben jullie ook ervaren. Heel veel dank voor de altijd fijne contacten.

Hooggeleerden Dhert, Castelein, de Putter en Raghoebar, dank voor uw bereidheid om zitting te nemen in de manuscriptcommissie en uw kritische taakopvatting.

Hooggeleerde Stoelinga, beste Paul, preprothetische chirurgie is ook altijd jouw interesse gebied geweest. Behalve deelname aan de manuscript commissie ook heel veel dank voor de waardevolle adviezen.

Anita Askamp, Sonja Beuker, dankzij jullie jarenlange nacontrole was het mogelijk om deze patiëntengroep te vervolgen. Heel veel dank daarvoor.

Wijlen Professor Dr. G.J. Kusen, stafleden en alle medewerkers van de afdeling Mondziekten en Kaakchirurgie in het Wilhelmina Gasthuis en het AMC in Amsterdam. Het was een voorrecht om op deze afdeling de opleiding te mogen krijgen en te werken. Nog steeds kijk ik hier met heel veel plezier op terug.

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Dankw

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Wijlen geleerde Brants, Jaap, eerst als coassistent, later als assistent in opleiding stimuleerde jij mijn belangstelling voor het vakgebied. Een echte mentor! Dit heeft uiteindelijk tot samenwerking in de maatschap geleid. Helaas is dit maar van korte duur geweest.

Geleerde van den Berg, beste Tom, als één van de eersten opgeleid in ons vakgebied vestigde jij je eerst in Arnhem, later in Bennekom. Om in zo’n goed lopende praktijk te starten was een waar genoegen.

Zeergeleerde Bolouri, geleerde de Lange, beste Susanne en Machiel, samen met Peter vormen wij een dynamische maatschap. Jullie inzet voor de dagelijkse werkzaamheden, maar ook de ambitie om nieuwe dingen te ontwikkelen en daarmee naar buiten te treden, maakt, dat met veel plezier gewerkt kan worden.

Dames van de afdelingen Mondziekten, Kaak- en Aangezichtschirurgie in het ziekenhuis Gelderse Vallei in Ede en het ziekenhuis Rivierenland in Tiel, hartelijk dank voor jullie professionele inzet iedere dag weer. Zo’n goed team en de goede sfeer maakt, dat het werken een genoegen is.

Operatieassistenten en medewerkers van het OK-complex ziekenhuis Gelderse Vallei, dank voor jullie hulp, meedenken en belangstelling bij het uitvoeren van de distractie ingrepen.

Greet, 39 jaar samen, rots in de branding, zonder jouw humor, nuchterheid en steun in goede én in slechte tijden was het allemaal niet gelukt. Oneindig bedankt!

Reinier en Arthur, fijn dat jullie er zijn.

Curriculum Vitae

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Curriculum Vitae

Frits Perdijk werd geboren op 18 augustus 1949 te Rotterdam. HBS-B diploma werd behaald aan het Montessori Lyceum in Rotterdam.

Vervolgens werd de militaire dienstplicht vervuld bij het korps geneeskundige troepen van de Koninklijke Landmacht.

De studie tandheelkunde werd gevolgd aan de Universiteit van Amsterdam. Hierna werd gewerkt als tandarts algemeen practicus bij het AZIVO ziekenfonds in Den Haag en Scheveningen.

Specialisatie Mondziekten en Kaakchirurgie in het Wilhelmina Gasthuis en het AMC in Amsterdam. Opleider: Prof. Dr. G.J. Kusen. 1980-1984.Hoofd van de polikliniek Kaakchirurgie AMC van 1984-1988.

In 1988 werd toegetreden tot de maatschap Kaakchirurgie van het Prot. Chr. Streekziekenhuis in Bennekom, voorloper van de huidige maatschappen Mondziekten, Kaak- en Aangezichtschirurgie van het Ziekenhuis Gelderse Vallei in Ede en het Ziekenhuis Rivierenland in Tiel.

Frits Perdijk is getrouwd met Greet van Bruggen. Er zijn drie zonen geboren, Reinier (1980) , Viktor (1982-1999), Arthur (1987).

Perdijk

verklaring: Geografische naam, afgeleid van het toponiem Paradieck, een hoeve gelegen tussen Diepholz en Vechta in Niedersachsen (Dld.). Het element diek betekent hier waarschijnlijk ‘waterplas’ en het toponiem wordt wel verklaard als ‘wed (drinkplaats) voor paarden

eerste naamsvermeldingen:• In 1758 vestigde Dirk Jansz Perdijk zich in Reeuwijk. Dirk (Dietrich) was in 1719 in Mariendrebber (in de omgeving van Paradieck) gedoopt als zoon van Johann Heinrich Pardieck .

promotoren: prof. dr. g.j. meijer & prof. dr. r. koole

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